League of Legends (LoL) Question: how do i farm well?

know what and when to auto attack and not(yes both of them have pros and cons).
practice.
map awareness.
communicate and be more team-oriented(know when your teammates need to farm in that lane badly over you).
have fun, never rage whenever someone takes your farm, it'll cost you more. the game's supposed to bring you fun not stress! :D

There's no real way to learn how farm well, it's about knowing your champion's damage at level 1 and what it can do to a minion. To actually farm well, you must time the damage dealt to the target per second and strike at the right time. A good example is a 100/500 hp minion being dealt 5 damage per second, you deal 50 damage, you would wait 10 seconds and then attack the target.

- Play champs that are easy to last hit with or have farming abilities that don't cost a lot of mana (Annie, Miss Fortune, Varus, Karthus, Nasus, Ezreal, etc.)
- Practicing in custom games can work sometimes so try that out
- Just keep practicing and cs-ing will become natural for you

Just practice last hitting in a custom game. Easiest way to do this is pick one of your preferred AD's and don't buy any items and just last hit. A goal you should set for your self is ~80 cs every 10 minutes.