Ok here's a few basic errors that I am seeing a lot of at the minute, if you're doing these then stop!
1) Not listening to what she's really saying to you (This is my real pet peeve)
A big problem I seem to see is guys not paying attention to the neon signs of sub-text staring them in the face when texting a girl.
If a girl rejects an invite and doesn't suggest an alternate time to re-arrange then she is saying "I'm not attracted to you enough to go on a date" NOT "lets totally do it another time".
If a girl says "I don't want to be in a relationship right now" she MEANS "I don't want to date you" the "right now" is a courtesy to soften the blow not an affirmative declaration that she's going to marry you further down the line!
2) Phoning a girl you've never been out with
Nobody likes speaking to people they barely know on the phone, it's awkward and invasive. Text a girl to set a date.
3) Bombarding her with texts
If you're texting a girl it's okay to have a few rapid fire text exchanges but you want to eject before the conversation gets stale, go out on a high!
Also space your texts out once in a while, if you're busy do something else before you text back.
4) Asking permission I don't mean become a rapist
A lot of people are asking a girls permission to do stuff; this is beta. An alpha commands what he wants. If you're saying things like "would you like to...?", "do you fancy...?", "are you free...?" slap your hand and flush that iphone down the toilet.
This should be obvious to most, but there seem to be a lot of people attached to a single girl... If you do this then you'll kill your chances because you will inevitably come across as far too keen and needy.
It's the paradox of appearing both interested and disinterested at the same time to build attraction and keep her guessing.