i had to do something similiar when i took speech and they covered debate. part of the coarse was defending stuff that you may not personally support or don't care about. one advantage you should have though and that you should use is that since your not progun control you should be able to have a good idea of what your opponet might say. try taking the defense there. i take it your not the affirmative. so a more defensive strategy might be better anyways.
i think one benefit of this exercise is to try to learn to see things from your opponents perspective and to try to use that in your debate. think of what you've heard gun control people tell you before, and figure that's what your opponents will expect you to say. then try to avoid saying that. as far as pro gun control information, try reverse engineering nra papers. then you can site them adding extra strength to your arguement. use techniques used by the media, you just delete what doesn't support your arguement. focus on what does. jsut keep good notes, they'll probably try to call you on it.
i've previously tried to find information on both sides. this will be another strength for you. you'll notice certain studies will tend to dominate most resources. i'm assuming that your at a high school level which will make that even more so. try your local search engine, that's most likely what your oppostion will do. anything that stands out on multiple occasions is a good object for scrutny, see if you can find flaws in those studies, if your opponent uses any of them, then don't hesitate to point those out during a rebuttal.
one good thing i've learned from english is how to manipulate information to really biase it. this is basically the same technique the media uses. it's not really lying, but it's not telling the truth either.
wew, that's about all the debating addvice i can think of. i'm trying to pass this on from experience in a similiar situation, i've allways prefered to try to focus on a good strategy, just don't get locked into one, you'll have to be flexable, you'll probably notice a few people if your at a typical highschool level, try to rebut things that nobody stated.