I was there in 2007, luckily I was staying in a house that was right on the course
awesome is an understatement
Anywhere on the course is good, just depends if you want the town area for bikes racing through the streets or you want fast open roads etc
I viewed it at the end of the starting straight just where they take a right hander to head out through the town, further up that particular bit is a nice place near a pub etc.
There's also the actual start/finish point where you'll see the pitstops etc.
The bit where they jump over the bridge as well.
And of course the mountain section.
The choices are endless just depends what tickles your fancy
I'm hopeless at remembering the names of these places but if you go on YouTube I'm sure you'll catch videos and suss out the places you want to be.
And of course a MUST DO is ride the actual route, I think I took about a day to go round it but I wasn't there to do it faster than the next guy, I just wanted to do it and get the t-shirt
Other things to do is make sure you get down to Douglas in the evening as there's loads going on.
I'm saving up to try and go again in a few years time.
Enjoy yerself young man