1. You'll probably get quite a few opinions on particular brands and models - in the Northeast a lot of people swear by Vanson, and a few swear at them. I've bought a $300 eBay suit and crashed in it and it was fine. I have a Kobe suit now and it sucks. You'll want good ventilation (you can always add a windbreaker underneath it in cooler weather), good YKK zippers, and CE armour in elbows and shoulders. Most suits have single zippers in front, but some people prefer 2 zippers so the front can be opened completely between sessions (makes chest protectors easier to deal with too).
2. Invest in good boots. Ankle and foot injuries suck. Sidi's are great boots, but they run narrow, so if you have wide feet, I'd consider A*. I've heard good things about the Supertech-R's.
3. The website of whoever you ride with will tell you what's needed for your bike and for yourself. It varies by track day organization. I ride with Tony's Track Days and the requirements are removing or taping all glass - mirrors, headlight, removing or taping the tailight/brakelight, and good tires, brake pads, no oil leaks, etc. Replacing coolant with water is preferred but not mandatory. It's a good idea to go over your bike before the trackday to check for loose bolts, etc. If you're doing a lot of trackdays, you'll probably want to safety wire the bike.
For a new track day rider DOT tires are OK. If you're doing 1-2 days/month, you'll go through those pretty quickly. You can replace with stickier but still DOT legal tires, or go with slicks. If you get slicks, consider tire warmers (and stands).
Other stuff you didn't ask about - a back protector and I'd strongly recommend a chest protector too. Since you're planning on a lot a track days, consider a set of spare wheels with rains mounted, and rain gear including glove and boot covers.
I hope this helps!