From my past experience in letting my B12 sit around too much between rides.....
Get a spare set of plugs. You may not need them right away, but you'll have them.
Charge the battery. If you can buy a battery maintainer type, like a BatteryTender, that's cool, but any small battery charger will work, preferably not more than one amp.
Fresh gas doesn't hurt. If you're in doubt of the age of the gas, or it's quality, drain the tank, and the carbs, and refill with fresh stuff.
You can also add a little techron or carb cleaner type stuff.
For the heck of it, and for familiarisation purposes....I'd check the air cleaner.
You'd also want to pull the plug out of the drain hose from the airbox, and let whatever is in there drain out.
If you've had the tank off the bike, maybe the hoses are on wrong?
(Or pinched....)
I'd do all of the above, and try to start the bike. If it doesn't start, you can check/change the plugs.
Are you using the choke? The Bandits seem to like the choke used to start 99.9% of the time.