Farming is the act of a champion killing multiple minions to gain gold. Certain champions have abilities which aid them in farming. Farming early game will allow you to purchase better items, making your late game stronger. Later in the game, farming opportunities will be fewer.
Farming is an essential component of early-game laning. Champions try to out-farm the enemy and "win" the lane.
How to Farm
The aim is to achieve more "CS", which stands for "Creep Score", which represents how many minions/monsters you have killed. You only receive gold and CS for "last-hitting" the minion/monster. This means that you should always try to get the killing blow on minions.
This is the main phase for farming. Many champions have abilities which aid farming, either by making it easier to land the killing hit (eg. Annie's Disintegrate), or by granting extra gold, such as Gangplank's Parrrley, Twisted Fate's Loaded Dice or Ashe's Hawkshot.
It is harder to get CS when your lane is pushed to your tower, since the turret's attacks are stronger than your own, causing it to kill many minions. On the other hand, you can push the lane to the opponent's tower, where they will lose CS. However, this is risky, as it opens the lane up to ganks.
When teamfights begin, gold will come from killing champions, lane minions, and clearing the jungle monster camps. When possible, lanes can still be farmed, though your absence can hurt your team in a teamfight.
Now the game will mainly focus on teamfights, meaning that farming is secondary. Despite this, minion waves will slowly accumulate (usually in side lanes where teamfights are not taking place). These can provide large gold/experience boosts, though as stated before, your absence can potentially hurt your team.
Many players underestimate the value of farming creep kills. The following table displays how much gold can be earned when you kill all minions in your lane.
This table is theoretical. The table below ignores travel time of minions in order to prevent a bias of lane positioning and can be seen as an absolute maximum for creep score. To use it in reality, estimate the Creep Score you will have and you can calculate the gold you have without kills. You can do this for certain points in the game (e.g. first time back, beginning of mid game) and optimize your item build. This table was produced and posted originally on the league of legends forums by bluebaron201.
Another alternative is to use the Creep Score Calculator, which allows for more interactivity. This tool was produced and posted to Reddit by TheMullinator.
- The table calculates the spawned minons, but it does ignores the travel time to the lane. On bot lane at 10 minutes the maximun number of minions killed will be 101 (48 melee minions, 48 ranged minions and 5 siege minions) there will be a creep wave passing it's teams tower in the 10 minute mark, I did not count those.