I've found that not scratching a mosquito bite when it's fresh means that it stops itching fairly quickly and completely. The red mark takes just as long to go away, though.
I have no idea whether this generalizes to other people.
Not scratching, huh? That takes an awful lot of willpower, but I'll give it a go.
If it's worth saying, but not worth its own post, even in Discussion, it goes here.