Getting Ready to put Carbs back into the bike today, I have a couple float questions.  I see how to check the float height, but how do you adjust it if its not even??  How difficult is it to get these even?? Should I expect not to be even the first try?  Will I be able to tell they're not even immediately after the bike starts??

Here's how to actually adjust the height

http://cgi.stanford.edu/~sanjayd/gs500/Maintenance/FloatHeight

I plan on doing this in a few weeks, but I've never done it before. So I can't answer any of your other questions, sorry.

They are easy I put them on mu chest and tip forward with the famous ruler on the side of it. I actually had a small piece of a ruler with the exact level welded up with a L shape ... but lost it a few months ago. Now, back to ruler.
Cool.
Buddha.

But beware, your float height (GS500F right??? ) must be 13mm + - 1mm.

when measuring u start tilting the carb untill it barely touches the needle right? because if u go all the way upside down u compress the system right?

Yeap! Thats right! 

anything else i should be checking for when the carbs are off? im new to bikes but if i leaved it in prime gas pours out the intake ad i was told my floats where wrong. anything else?

When adjusting the float height remember 14.6mm for pre '01 bikes and 13mm thereon.
I would check the needle valve, for the flooding issue.
Also try cleaning the jets, always a good practice.