try to have 8-10 cs in a minute. try freezing a lane and farming it trying to last hit every minion. if I'm behind by my teammates seem to be reasonably defending towers without me, I take the time to freeze a lane and farm. I pay attention to the items that give me a power spike instead of my farm. I mean I do try to improve my farming every game, but I know when I have the damage to help my team and when I don't, and I focus on that during a game. by the end of the game, I'm surprised sometimes at how well-farmed I was, because I focused on the shorter-term goals to do so, for example I need 500 gold for IE, for example.
and also, the most important thing, is objective control, and grouping. sometimes your team has to sacrifice CS in order to siege or defend an objective. but be wary of these times; if one team is farming while the other is sieging, the long game will go to the farming game. so if your enemies are trying to farm and you don't think your team will take an objective within 30 seconds, call off the siege.
don't chase a kill. if you can finish someone off with just 5-10 seconds of a chase, that is fine, but if 5-10 seconds pass and you haven't secured the kill, find a better target. maybe an ally needs help fighting someone, maybe there is 6 or more minions to clear nearby, maybe you can pressure a tower (preferably with allies nearby or vision). if it's a fight over dragon and the enemy has taken serious damage, then rather than chase them start dragon. if they're foolish enough to try to contest, then you can finish them off, or at the very least zone them out while your jungler finishes off the dragon.
and, even if there isn't any minions to clear right off the bat, executing plays quickly allow you to farm creeps sooner, especially if you need to recall first. if a play takes too long to execute, the enemies who've recalled will show up and pressure something you can't defend. and lost farm is lost farm, even a large wave represents a significant loss in minions as the wave accumulated. so chasing a kill will ultimate leave you behind over the course of the game. especially if you die chasing it :( Ideally you should make a play as a team, then farm up a bit, then make a new play. if you're making play after play, you're sacrificing farm; so if you can avoid that do, and if you can't remember that that means you're playing for the early pressure and a quick endgame.
