You've been given a lot of advice, but here's mine. The top three "thrill rides" (term used loosely) at Epcot are Soarin', Test Track, and Mission Space. Out of those three, the longest wait times are divided between Test Track and Soarin'. Mission Space has almost always been a 10 minute wait or less when I was there while those other two were over an hour at least.
So if the two you most want to get on are Soarin and MS, I'd run to the Soarin area. If the lines are less than 20 minutes. Go ahead and jump in line because they won't last like that long. By mid day they'll be long. If they're over 20 minutes then grab a fast pass. Check the return time on the Fast Pass, it'll probably be somewhere after 10:30.
If you use the standby line for Soarin, after you're done there stop by Test Track and check out the lines there. If they're short, go ahead and hop in line, if not grab a fast pass and head over to Mission Space, then come back later to do your fastpass ride on Test Track.
If you grab a fast pass for Soarin', then head over to Test Track and check out the lines (it's on the way to Mission Space anyhow.) If the lines are short, go ahead and jump in line. If not, head on over to Mission Space for standby which still shouldn't be more than 20 minutes max. Then head back for your fastpass ride on Soarin. Then go grab your fastpasses for Test Track if the lines are still long and enjoy the rest of the park while you wait for the fast passes there.
I know that was complex, but it makes sense to me. Either way, I would grab your fastpasses for either Soarin or TT first because those lines can get really long. I've never seen MS over 20 minutes, but who knows if the new version of the ride will make that line longer or not.