With the Fast Passes, let’s say you want to ride Monster’s Hide and Go Seek but see a looong line in front of you, check out if the ride has a Fast Pass System and see what time the system is allotting at the moment. Get the Fast Pass and come back to the time designated to you. For example, you’re get to Monster’s Inc ride and Go seek at 9:30, line is long, so you check the Fast Pass. You see that the schedule for the Fast Pass is at 11:30-12:30 and this is good with your own schedule (no shows to watch, no parades you want to go to at that time), grab a Fast Pass using your Disney Tickets. You may now go and try out/line up for the other rides. Come back between 11:30 and 12:30 and you can now use the Fast Pass line which will usually take you straight to the ride or with very, very minimal time of waiting.
The Fast Pass ticket you get will also tell you when you can get another Fast Pass Ticket.
In the example above, it might tell you that you can get another Fast Pass Ticket after 10:30. So what I usually do is get another Fast Pass Ticket to another ride, say “Space Mountain”, by 10:30. Thus, we get to maximize our time doing something else and minimize waiting times for other rides. You then have 2 sets of Fast Pass Tickets!
Scheduling and the Fast Pass system is very important or you’ll end up wasting a lot of time lining up.