Here is a map of where you can and cannot park in Grenoble during the tour - I could find it only in French - [original link]

For the mountain stages you would need a car or to book some sort of tour package similar to this - [original link] or here are some hotels that are supposed to be close to places the tour passes through - [original link] .

Be aware that if you take your car, the road closures are early and it's hard to get a good spot. Also you will be standing around for possibly hours, so do not forget drinks and food for yourselves and sun cream or umbrellas depending on the weather. Leaving is insane by the way - everyone piles into their cars and gets into an immediate traffic jam once the gendarmes announce the final racers have passed and the roads open again - don't count on any police to sort it out, just be patient.

For watching, don't pick a downhill - you will only see the racers for a brief instant. Try to find a climb up a hill if you want a chance to see the racers for the time it takes to identify them.
Enjoy !