Using Fast Pass will need serious planning before you even go on your trip to WDW. The Magic Kingdom is a Fast Pass "Heaven". I'm going to give a senerio and please tell me your opinion. First of all I think Disney is vague in how they describe Fast Pass so it is much better to hear from people who have used it, rather than just reading it out of a brochure.
We arrive at WDW shortly before it opens up. We are at the MK, and it is a moderate day and time of the year for reasonable crowds. The gates open. BAM! We decide to look at the MK like a wheel. We know that we can go back to Main Street U.S.A. the front gates, monorail, castle etc when we are done with the rest of the park. So we start to go to the castle, then we take a left toward adventure land. If Pirates is open we make a dash to there without using fast pass. Probably wait a little and maybe make 2 times on the ride. Reasonable. Then we head on over to the jungle cruise and tiki room which aren't that packed yet. Do those just once, look around a bit at the shops and architecture and then head on over to F L.
We try to see which ride is more packed SM or BTMR. Which ever one is more packed we put in the fast pass and head on over and wait normally for the other ride. We can enjoy the architecture, etc. After that we wait for our window of opp which will soon be coming we can take that time to browse around FL look at the architecture restaurants shops etc. Our time comes we board the other ride, we don't have to run we have within an hour to do this ride and we are already n the que line. We do the ride finish FL and head on over to Liberty Square. We put in our Fast Pass for the Hall of Presidents cause the lines are picking up. waiting for that window of time we can do the call of nature, eat, and relax and enjoy the people watching that can only be done at liberty square
We do the hall of pres, finish Liberty Square, the parade will be starting soon I guess, and we head on over to Fantasy Land. This is an older party not little kids. Fantasy Land would be packed by now because you have people like us who started from AL and worked our way to FL, and you got people from TL working their way over to FL. Plus the people who just walk straight into FL from the entrance.
Could someone confirm if It's A Small World uses fast pass or not? I hear that ride gets packed by afternoon. So we can wait for IASW if we have to. We can listen to the song over and over and enjoy the funky pastel colors in the que line. We board do the ride... done. We do the call of nature one more time after listening to that beautiful world's fair song over and over...
Since we are older we don't need to go into the other pavilions and rides. We have all ready eaten, etc. Maybe go to PhilarMagic, but that's it. We can take our time and enjoy the architecture of fantasyland. We'll skip Toontown. Its to kiddie and too packed, plus we have already done that last time we were at WDW. We head on over to TL. This is probably late afternoon possibly. We work our way over to Space Mountain punch in fast pass, we can walk around and enjoy the half 1971 architecure of tomorrowland and the other 1995 architecture of tomorrowland. Two in One!

While we wait for SM. We can browse the restaurant and shops, do some more people watching, and then become a people mover on the TTA which is never a long line. A nice pleasent sit down ride will do us good, and will be great for getting pics and video of tomorrowland. After that our time should be coming up and we head on over to SM. Walk down the que at a reasonable pace since we have an hour to get on the ride. Do that...done. Head on over to CoP. Enjoy some world's fair nastalgia. Maybe go to the time keeper after if we feel like it. We then exit tomorrowland toward the castle. Stop and rest in that little park. Go inside the castle etc. Go see the chrystal palace, go back through Main Street U.S.A. do what can be done there, and some window shopping of if necessary. Then take the monorail or train to take it all in. The train for MK, the monorail for the almost the whole resort. It's a nice way to end your day. Then exit the park through the MK entrance.
We didn't mention seing the parade and we probably wouldn't. Welve been to many parades and don't necessarily need to any more. Plus we will be out of there before the park crams for the fireworks which we have seen before.
Sound good?