How do I stop being the "best friend" type to girls?

Learn to flirt properly... I guess..

Don't be so "available". If you like a girl and feel the zoning coming on, move on. They love what they can't have.

ask somoene you like out, learn to flirt, look for someone who can set you up on a date,go on a dating cite and see what women like in partners, what makes them view men as partners. there are probably other thing but this is what first came to mind.

By hitting that very small window between knowing a girl better and becoming her friend. Girls have some magical barrier where they can't date male friends. That or it's a lie so they don't turn you down more harshly. But in any case if you just let it go and not flirt with a girl for a certain time you will get yourself a one way ticket to Friend zone-ville.

Become attractive

Be more honest about what it is you want. Women aren't mind readers.

Be forward and express your expectations and needs.

You have to tell her

The intention, yours, is fully in what you do and decline to do, never in what you think.
The real meaning of what you say is fully on what your listeners understand.
Own the results or change.

The friend zone sucks she don't want a relationship with you cause it will mess up your friendship, like her ripping your heart out and shitting on won't ruin the friendship.

Truly stop caring about it first I'd say and focus on your own life like your dreams, ambitions or ideas of fun.

Ladder Theory would apply in your current situation
http://www.laddertheory.com/

Don't be friends with them unless they put out

Give an ultimatum.

Stop being so nice to them and stop being there for them when their badboy boyfriends treat them like shit