When you go to Universal Studios, quickly do Shrek and Jimmy Neutron first because they get crowded quickly (since they are up front AND new). After that run over to Men in Black on the opposite side of the park and ride that a few times until you are satisfied with your score then do Back to the Future and then whatever else you want.
The reason I say this is Men in Black's Express line sometimes gets REALLY backed up. This isn't always the case, however, near lunch time and afternoon, that's when the people over at Shrek and Jimmy Neutron have made their way over to MIB. This way, if you have done MIB a few times, you can always go back, but if you don't want to wait in a long line, you have already done it.
I always do it this way (actually I just skip Shrek and J. Neutron and go straight to MIB) and ride MIB 6 or 7 times, plus BTTF all before 11 AM!!! And that's when getting inside the park 30 minutes after it opens.
Later in the day I've found the wait to be way too long. Even single riders can be up to 20 minutes!
But, again, it's not always the case. Find out what most interests you and go from there. Keep in mind what rides are the newest (MIB is still fairly new...only J. Neutron and Shrek are newer...right??) and go from there.
Have fun!