All of Tristana's skills have high cooldowns early on. Be wary of trading while they're on cooldown.
Leveling Rapid Fire early on is unadvised, since her low base Attack Damage early on the game can't make much use of the AS steroid. Wait until you buy some AD items such as a B. F. Sword.
Rapid Fire is applied to the next autoattack's wait period - cast it right before an autoattack to squeeze as much as you can from the duration.
Since Rocket Jump resets on kills or assists, you may use it to secure a kill and to either jump out of a deadly situation or jump again to set up another.
The cost of Rocket Jump is a bit high compared to her mana pool. Make sure you have enough mana to use it at all times.
As many players tend to level up Explosive Charge over Rocket Jump, be mindful of its long cooldown at rank 1 as jumping into a bad situation without getting the reset may end up just getting you killed.
Tristana can use abilities while in the air during Rocket Jump. This allows a very strong and fast combo if you play her as an AP caster.
Using Rocket Jump to leap over an enemy and then using Buster Shot to send them flying back to your allies or an allied turret can be very effective, but be careful about using the strategy in large team fights.
Be careful when using Rocket Jump as it is considered a "dash", even though it is visually a "jump". This means that if you jump over a trap (like Yordle Snap Trap) you will activate the trap and its effects.
Likewise, this also means that many enemy abilities such as Thresh'sFlay can interrupt your jump mid-flight if you're not careful.
The passive of Explosive Charge is particularly useful in farming - if there are a lot of minions in a relatively confined area, killing one could burst the remaining minions and gain a lot of gold in a relatively short time, without the use of abilities.
Combine this with Rapid Fire and she can easily farm up and clear minion waves with an ease. Be aware that this may push your lane more than necessary and leave you open during the laning phase.
Explosive Charge can be used on turrets. Use this to your advantage when given the chance to push the lane.
Explosive Charge resets your auto attack animation, allowing you to sneak in another auto-attack to push trades in your favor. In addition, landing four autoattacks will automatically detonate the charge and deal large amounts of damage
You can also detonate the Explosive Charge charge by jumping into the enemy using Rocket Jump after you have landed three autoattacks on them. This is useful if you are paired with a support that can lock down your target like Morgana, Alistar, Taric, Thresh, and Leona. However, keep in note that this is a high-risk/high-reward move and can put Tristana in a more vulnerable position.
Tristana's low base movement speed makes it difficult for her to chase enemies or to escape. This is especially prominent at low levels. Getting Boots of Speed quickly is highly beneficial. Be sure to watch the enemy builds and pick the proper boot upgrade.
A The Black Cleaver is a good item to build on Tristana, as it not only gives her some cooldown reduction, but synergizes well with her Explosive Charge. After four basic attacks, the target would already have taken about 4 stacks of the item's passive and have taken even larger burst of damage thanks to the armor shred. It's best to land one or two basic attacks before landing the Explosive Charge charge on your target.
Trinity Force is a extremely situational item to build on her. Its substantial cooldown reduction is beneficial for her Explosive Charge, she can continuously proc Sheen's passive for roughly every 7 seconds at higher ranks, and the Phage passive can be useful when kiting enemies. However,Tristana has a low base Attack Damage, so Sheen's passive is not as effective. There are a variety of attack speed items which also give critical strike chance, an important stat on Tristana, such as Runaan's Hurricane or Rapid Firecannon which give movespeed for kiting.
Essence Reaver is not an escpecially great item for Tristana. While it gives mana sustain through critical hits, and also some cooldown reduction in conjunction with any attack speed and critical chance item, allowing her to use Explosive Charge more often, Tristana relies mostly on her autoattacks and so Infinity Edge is a better alternative.
Be careful when picking Tristana, as an enemy's blind can render you fairly useless. A Quicksilver Sash can be used to counter blinding champions such as Teemo and to escape other hard CC.
Wit's End, while unconventional and lacks flat AD components, can be quite useful due to Tristana's emphasis on basic attacks, with the extra MR providing her with defense against casters and the MR shred allowing her abilities to deal more damage. However, it should not be built until later since Tristana's early game is weaker than most marksmen.
Due to the high ratios on her abilities, APTristana can be built if your team requires an AP nuker, as well as an AP support due to being ranged with decent crowd control capabilities.
Tristana loses her DPS potential with a full-AP build, but gains newfound burst damage to whittle down targets and in teamfights, she can potentially one-shot them. However, this type of build offers very risky gameplay, as Tristana must make sure to play safe due to lack of strong-auto attacks, as well as her general squishiness.
Lich Bane is also great item for her AP build, as you can get in extra proc from your Rapid Fire.
Like with Lich Bane, Nashor's Tooth in combo with it can not only provide cooldown reduction and attack speed for Tristana to retain DPS, but due to the procs scaling off her AP, it can make up for her lost ADC style.
Tristana is an AD-carry with massive base damage on 3 of her spells giving her a very powerful early game. However, when built AD, she does not have scaling for her burst abilities due to the lack of ability power, meaning her mid-game is a little weak. Abuse this, since Tristana late game is one of the closest to unstoppable in the entire league due to her massive range, AS-boost and peeling power of Rocket Jump and her ultimate. DO NOT underestimate her though, as even with a "weak" mid-game, she can and does have decent burst when done right, and any decent Tristana player will be working to compensate for this.
Tristana is notorious for her ability to reposition to safety with a well-placed Rocket Jump. As this resets on kills and assists, having allies fall to her can make pinning her down difficult. It has a long cooldown otherwise, making it best to cripple her mobility or damage so she can't make use of it.
Tristana has a huge auto attack range when she reaches level 18 because of her Draw a Bead; avoid getting kited.
Early game, her range is fairly short; use it to your advantage to harass her and deny her farm.
Tristana has a lot of burst damage from her abilities early on - buying early defenses along with having a way to escape her/peel her from you can hinder her from zoning or killing you at the early game. A target surviving her abilities being cast on them leaves her vulnerable to counter-attacks if they have the health or sustain to stick around.
That being said, champions with larger burst combos such as Lucian, Graves, and Ezreal can win trades easier if the aggression is timed correctly.
Standing near the brush can allow you to duck into it after she uses Rocket Jump on you, avoiding a good follow-up from the rest of her abilities. As Rocket Jump is the lynch-pin to her combo, she can then be attacked from range after escaping her without fear of reprisal while it is on cooldown.
During the laning phase, try to bait out Rapid Fire as she can only damage you with her auto-attacks and Explosive Charge if she plans on saving Rocket Jump to escape. It is optimal to force aggression on her after the duration since she does not have many options to retaliate aside from her support.
Tristana has no long-range poke abilities - having a champion that can do this can damage her freely.
As the range of Rocket Jump is very long, however, being a champion that can escape or having a partner that can peel that is likely also a requirement.
Tristana is vulnerable to being hit by skillshots during the animation of Rocket Jump (being essentially a very slow dash) and hard crowd control can stop the ability entirely while it is casting, returning her to where she started.
Move away from a low health minion at early game to avoid the damage from her Explosive Charge's passive.
Tristana mainly deals damage from her auto-attacks. Randuin's Omen and Frozen Heart are good options to counter build against her, since it will greatly reduce her damage per second output. A Thornmail will counter her damage, but generally is a less better option since it helps to defend only yourself.
Try to not engage her when she can easily escape with her Rocket Jump and Buster Shot off cooldown. The exception is when you can hold her in place with crowd control long enough to kill her.
If Tristana is building AP, be very cautious and ward well as she may jump out of nowhere and one-shot you easily. Also, missing calls can prevent a lot of her potential ganks.
In team fights, do not leave any squishy teammates in the front and prepare some CC for her all-in. Be sure to back away if your team have multiple low health allies. She may get multiple kills because the cooldown of Rocket Jump resets whenever she gets a kill or assist.
Purchasing a Banshee's Veil counter AP Tristana easily, as it negates one of her spells. Because AP Tristana is combo reliant and she has long cooldowns, if she can't kill you, she becomes useless for a time; if you negate one of her spells, a huge portion of her damage is gone.
Kog'Maw and Jinx can effectively counter Tristana late game as their basic attacks not only outrange Tristana, they also have better lategame damage scaling than her.
However, Tristana is considered to be the best turret destroyer thanks to Explosive Charge as well as incredibly good at securing objectives such Dragon and Baron Nashor. Combined with Rapid Fire and reasonable attack damage and attack speed items such as Youmuu's Ghostblade, Infinity Edge, and The Bloodthirster, she wither down a single turret's health to more than half it's health. Do not let Tristana anywhere near a turret. If Tristana is missing in action, chances are that she may be hiding somewhere and her team might be buying her time to effectively split-push and destroy a turret.
When laning against Tristana, try to push the wave because the passive of Explosive Charge will damage minions and make it harder to farm under turret. She cannot freeze the wave easily because of this as well.