Try this trick before getting into a PvP game.
Go into customs, and set up a 1v5 with bots.
I started this because I sometimes have random ping spikes. I usually did bot games before I went into a real game, but once I had a horrible lag and disconnected out of a game just before the game ended. So, I started playing customs before a real game. It got boring just practicing CS alone, so I started adding 5 bots each match.
So, I'd go into a custom game, set up a 1v5, go mid lane and rush
or
, and get tons of kills before I proceeded to destroy their base by myself.