Something simple for your first mike. unscrew your starter switch assembly on your handlebars and clean the copper contacts. My 1982 GS550 Kat that I got this spring, got sold to me at a great price because the guy couldn't get it started after just a winter of sitting covered outside. The reason turned out to be the contacts on the starter button were nicely corroded and not conducting power. Meanwhile, I had thought it was the solenoid and got me a "new" used one from a salvage place. I also went and got a new battery. Then, after starting it once, it didn't start the next time. So, I pulled apart the switch and checked for corrosion. Brushed it all off with some steel wool, and Voila... the starter motor got power and away I went.
Granted, I also bypassed all the elctrics and jumped directly to my starter motor (can do this with jumper cables if you need to), just to make sure my starter actually functioned. But, I'm willing to bet its your contacts in your starter switch.
As far as getting ignition after that... Once you get your starter spinning (if it isn't an electrical circuiting issue and is just corrosion), then you can check your plugs to see if they are getting spark. Did your bike sit all this time with a full tank of gas? Was it empty? Have you cleaned out your carbs completely? If not, you may not even be getting a good fuel/air mixture into your cylinders.
Good Luck.
