To change the habit, you have to decide to wait until at least the third or fourth date to have sex, and to monitor your conversation style to remove sexual hints and invitations. This is not so easy to do, but it can be done. You have to begin with a conversation with yourself, about what you want right now, and what you want for real. "Asking for What You Want" will show you the difference between immediate gratification (one night stand) and long-term satisfaction (relationship).
Understand which one you're going for. If you just want a quickie, fine, there's nothing wrong with it. But, know it means the relationship will go no farther. Usually, it's too difficult to figure out if you want a real relationship on one date, so that's why I say have at least four or five dates, to give you an idea of who this woman is, and whether you'd like a real relationship with her.
Do different things on your dates than you've been doing. Do your usual dates involve drinking? This lowers inhibitions, and makes sex more likely. Do you invite women home with you, or go to their home? That also increases the odds that you'll have sex right away. Instead, take a date somewhere different. Avoid bars. Try a little neighborhood restaurant, and limit yourself to a glass of wine.
For a second date, invite the woman to take a walk somewhere (a nice park, a zoo, a museum) or take her to a ball game (the local college game is cheaper than a pro game, and usually more fun.) Figure out what you're interested in, and try sharing that. If the two of you have similar interests, you're more likely to be compatible.
Perhaps you need to change where you're finding women in the first place: my article "The Fine Art of Squirrel Hunting" will give you some new ideas. The Unofficial Guide to Dating Again has more ideas on how to make your dating more successful.