I used to worry about mindset and would get myself in a confident frame of mind before talking with someone i'm really attracted to as to remain relaxed and not tense.
It worked for what i needed but at the same time isn't good confidence. It's drummed up, artificial and fleeting.
The best way i've found is to program your subconscious so your conscious mind doesn't need any 'pep' talks or this sort of thing.
Your subconscious affects everything, from body language to voice tone and your conscious thoughts. It's a more substantial long term form of confidence and comes across as such.
I can no longer worry about winning or losing (getting dates or rejections). I have somewhat of a perfectionist mentality (could come from programming too) in that i need feedback before making a next move. This can be good, but alot of the time you won't get the feedback you're looking for (or when you're looking for it). In essence, it's beta testing someone to see how they are. That's what dating is for and every trivial move should not be analyzed before dating as there is not enough information to begin with about the person (only through friends). Over-analyzing is good in problem-solving but is a disease of the mind when it comes to the opposite sex.
It's ok to look for some 'red-flags' as these are probably more obvious than anything, but leave it to the other person to let you find out more about them in what they like and dislike etc.
For me (maybe my standards and expectations are high) but i rarely find a girl i'm crazy about, and when i do - know it is few and far between so i'm more focused on getting with her than anyone. I think we all have this mindset to some degree as we all want to get and be with the object our affection.
To sum up this little rant, let go what you cannot control. Be yourself. Once knowing you have good confidence, being yourself becomes easier around those girls you like alot, because your insecurities are supressed or rooted out, allowing you to be more expressive with your personality.
I do recommend subliminal confidence mp3s. They're cheap to download and make a difference. It's like affirmations but for the sub-conscious mind.