I generally tell girls at some and repeat it a few times when the subject comes up "I don't do relationships, I find them restrictive and not what I'm looking for". Once this is clarified I find girls try even harder to get me into one, but I have the choice of where it goes and don't feel guilty. Funny topic, as I'm getting sucked into one at the moment, but kinda happy to do so, we make a really good couple and it's non pressured.