Well Mongo, I've been going every year since 1953, and I still get a thrill from the Island. In fact I was there only last weekend, and I had a really enjoyable weekend.
Anyway, most folk would say that you need transport. It's a big Island, and so much to see. It is fair to say that it is a BEAUTIFUL Island! Try and keep your mileage on the TT course to a minimum, buy an Ordanance survey map, and explore the place.
Can't miss sights? Calf of Man, Laxey Wheel, Niarbyl Bay, Peel Castle, Rushen Castle, there's a lot more, but it depends what you like. There are NINE golf courses, I find those attractive, not everyone does!
Douglas Prom at night during TT week is still pretty impressive, with lots going on, and little difficulty in finding a pub.
For viewing, you've got to watch at the bottom of Bray Hill at least once, once at the Grandstand, once at the Creg, and once at anywhere that tickles your fancy around the course. I always like the Gooseneck for the view.
If the weather is good, you're in for an unforgettable treat. You'll be asking yourself why you haven't been before!
Enjoy!