For me I have to do some extreme distraction! Usually watching messages online (lifechurch.tv), but sometimes I have to go out with friends. It's like when I'm completely alone that the enemy's able to wheedle my defenses away easiest.
Another point to throw out there, something I've been dealing with, is to be on guard! Temptation can be so sneaky. Even though I know that it's God's will for me to be single, in the past several weeks I've been asked out, my long-ago-ex has been calling me (I got the chance to witness, yay!), and someone I used to have a huge crush on is moving back in state.
I've never had to deal with so many gray areas in my life! With this kind of problem, praying for wisdom and staying immersed in the word are my failsafe tools.