The biggest mistake I see guys make, even when they're consciously trying to practice game, is that they commit to making a move but then pull back the reigns at the last minute. This often makes it look like they're trying to disguise their intentions, which makes them look insecure and dishonest.

The classic example: asking a girl out. A lot of guys will try to mask the fact that they're interested in the girl and asking her out. Instead of asking her directly, it comes out as "Hey, there's this thing I'm thinking about going to tomorrow...it sounds like a fun time...you could come...if you feel like it...but whatever." And then you try to pretend like you don't care whether she goes or not. (Which is bullshit, because if you really didn't care about whether she was going to go, you would have just asked outright, and been willing to accept the possibility she might say "no.")

Everything that you are, everything that you do, you have to own that shit. If you're sexually interested in a girl, don't act like you're ashamed of the fact that you're attracted to her. If you're going to approach a woman, commit to it fully. No half measures.