Choose your town where the TdF is starting. Usually the one closest to us. (We don't recommend watching along the route because all you see is brightly colored riders whiz by at a rate of knots. Additionally, unless you camp out very early the police won't let you get your car close at all.)
Go to the start. They don't start that early in the morning so you don't have to get up at the crack of dawn. Once in the starting town you can visit the shops to buy hats, t-shirts & whatnot as mementos. You can also visit the park where all the racing bikes are. You can get pretty close to them & the riders. Next you want to chose a spot where they will be riding by; you wait there for the 'caravan' (this is cars & trucks representing the sponsors) they'll have pretty girls throwing out goodies; bottles of water, candies, cheap hats & so forth. After the caravan the riders will appear. At this stage they're going slowly so you get a good look (I saw Lance Armstrong at a distance of three feet one year!)
Having done all of that its time for lunch. Over the years we've had some great lunches in the TdF towns. Surprisingly not many of the French book lunch so getting a table has never been an issue.
We've always found it to be a nice day out. This year, unfortunately, the closest starting town isn't all that close
David Hatfield