There is some really good stuff on the link kindly provided by the witch. My personal favourite watching spots (apart from in the saddle!) were the Grandstand, Glen Helen, Sulby, the Gooseneck (my top choice!), and the Bungalow.
Remember to buy/take a radio, because it is difficult/impossible to follow the race without one, unless you are under a speaker, and it is obviously a tad difficult to put them all round this magnificent island circuit. You may not have gathered that the competitors start in pairs at ten second intervals between pairs, so it is a bit like a time trial - without commentary the only way you can tell who is doing better than another is if, say number 56 comes past followed by 32 and 45 - they are running in unknown positions but 56 leads 45 who leads 32..........clear as mud maybe!
As far as the circuit is concerned, think of Spa x 9, but with much more variation and you begin to get it! - :wink: