tips for a mid laner ?

the video on getting better at cs'ing.

follow those instructions.

build to counter your lane, then the enemy comp. IE - mr against an enemy mid laner who needs to get kills to be a factor late game.

learn to gauge trades

Farm is a major part of mid lane, giving up farm for no reason is something you never want to do. Always think about how many waves you will lose when you do things like back or go for a gank. It also goes the opposite, if your enemy laner backs at a bad time or goes for a gank that you can't follow or you properly warn the side lane then shove the lane in and make him miss CS.

Also hitting 6 first (on most champions) is a huge advantage that will allow you to pick up solo kills if you take advantage of it effectively. Get to know how many minions it will take you to hit 6 and whether or not you will hit 6 first then try to all in the enemy laner when you hit 6 and he is still 5.

Depending on your champion, focus on farming rather then trying to harass your lane opponent. Also learn your champions power spikes. Learning the power spike can help you win your lane opponent. I'll use as an example. We all know her early game is relatively weak, but once she power spikes you can be surprised at how much damage she can do. You can surprise your opponent and potentially get a kill if they get cocky.

My second tip is to know when to back off and anticipate a gank. If your pushing a lane, never go past the insignia on the ground, because that means your over extended and you might die or burn summoners or both.

My third tip is to know your ganking potential as a mid laner. If your akali, or Katarina, and potentially Azir (Azir can set up NICE ganks if your good with his drifts), go roam. Roaming is one of I consider strongest part of a mid laner. Most mid laners have good mobility and since you have been in a solo lane, you would most likely be up in experience and gold. Roaming can help a losing bot lane or demolish the enemies bot lane. This can help secure a win.

Also, try to know where the enemy jungler starts, once you do try to know the outline of how fast they clear, that way you can ward the proper side of your lane and avoid ganks. I recommend warding either side of your lane around the 4 minute mark, since thats usually when junglers clear the jungle and start looking for ganks