The best way to negotiate is to have ammo. Yes another offer is nice, but that takes time. If you can go back to your projects that you've done for your company and say this is what I've done, and this is how it helped the company.
If you can put it in dollar figures, that's the best way. Maintaining your Microsoft partnership is a good example. Because of your certification, you're saving the company $XX in licenses.
IT encompasses a lot of things, a lot of which are considered support that don't directly charge to projects. So you can say you've satisfied so many tickets. If you know how many other people have done, and show you do more, that's even better.
If you get feedback and have a satisfaction rating, these are other good things to use.