On every fast pass there are 3 times. The two big print times are the times you are supposed to return between i.e. 3:10 and 4:10. However, of those two, only the start time matters. You can use a fast pass any time after the start time.
There is a 3rd time on the fast pass. It's at the bottom in small print. That is the next time you can GET a fast pass. In
Disneyland (and I assume it's the same in WDW) that time is usually 2 hours from the time you picked up the fast pass OR the start time of the fast pass, which ever is earlier.
So a big thing to do in HS is get there at rope drop, run to TSM and get a fast pass, ride it (if you want) because by the time you get off, you'll probably be ready to get another fast pass. You can hold onto the TSM fast pass and run over to RnR or ToT and pick up a fast pass there. Saving them both for later in the day.
At Disneyland, I would go to SM at opening, get a FP which would be for around 30-45 minutes later, ride it, then fo ride the Matterhorn. By the time I was done, I was able to get another fast pass for SM. Which I could give to my friend who wouldn't get to the park until 11 or so. This allowed us to ride it together and by the time he got there, I was able to get another fast pass for something else and he was able to get his first.
Also, I believe the 4 parks (MK, HS, AK, Epcot) run on their own fast pass system, so you can get a fast pass in one park and get another one in another park before your time from the first park is ready. The only thing you have to keep in mind is that the park tickets you are using to get a fast pass MUST have been used at the front gate to get in. So, you can't take your family's tickets, go to the park without them, and get fast passes.
Now for a tip: Everyone has been talking about "body glide" but I can't seem to find it in the stores around me. HOWEVER, I did find that BandAid makes an anti-friction stick that works wonders - CVS was carrying it. It's kinda small and meant to be used on the feet mostly, but it works on other parts of the body very well.