Read the suspension guide in the suspension section by tfaith. It's long, but worth it. Depending on your trails, you'll be looking towards xc or mx set ups.
Setup your caster, camber, ride height.
Alba front a arms, and the best suspension you can afford would help tremendously. Finding someone to revalve your rear shock would be beneficial or a fox, elka, ect.
If you need lots of ground clearance and increased traction go with 23" front tire and 22" rears. Otherwise, 21"/20" are easier to find and will handle better.
What is your current setup and budget?
I can help a little, tfaith and ddq are a lot more knowledgable about suspension.