Area 1: You'll begin in the control room near the hangar, helmetless.  Use
 the Force on the door to turn it into a TIE Fighter and move on out.  Use the
 helmet dispenser to get a stormtrooper helmet, which will allow you to access
 the doors with white circles.  Stand in the circle and press Z and the door
 will open.  Take out the troopers and officer (they may not attack just yet
 if your character is still wearing the helmet).  Assemble the two control
 panels and use the resulting Artoo panel.  At this point, Ben will take off to
 deactivate the tractor beam, Artoo and Threepio will hide in the closet, and
 it'll be up to the three remaining characters to finish this mission.  Head
 out the now open door to the left.

Area 2: Ben will run ahead of you.  Take out the troopers.  You can't follow
 him across the chasm, so go to the left.

Area 3: Blast them!  Note the helmet dispenser here.  Here's a trick I
 learned.  Being hit once will make you lose your helmet.  To prevent this,
 have a character take a helmet, then switch off to another character.  Since
 the one you control is generally in the lead, he'll take the most hits, so
 your helmet will be a lot safer.  This doesn't work 100% of the time, but it
 does give you better odds.  Anyway, move ahead and you'll find Ben being
 attacked by troopers.  Blast them all and he'll repay you by giving you a
 bridge to cross.  Once across, you'll find TIE pilots will be upon you by
 climbing up the catwalk.  If you shoot the hook they're using, they'll
 stop bugging you.  Take them out and blast the crates blocking your
 way.  Blast your way through the corridor and turn right at the end.

Area 4: In front of you is a white circle.  If you still have a helmet,
 quickly use it to open the door before the pilots come up and tag you.  Fight
 if you wish, or just pass through the door.

Area 5: At the center of this room, assemble the rotator switch, then use it
 to move the bridge.  Rotate it until it stops and you can climb up these
 ledges.  Blast the troopers and take a helmet if you need it, then pass
 through the door.

Area 6: Hmm.  Looks like they haven't noticed you, yet.  I say go to the door
 and assemble the panel so you can quickly use the helmet, then blast the
 bagoogies out of the place.  Continue on to the next room.  Take out the
 troopers here.  If you still have a helmet (or want to go back and get one),
 you can use it to access the near elevator and ride up to a Double Score
 Zone with a bunch of Beach Troopers.  Otherwise, take the far elevator down.  

Area 7: Blast the bad guys.  Also, take out the cameras over the elevators
 (they take about four clean shots) to prevent more troopers from coming.  
 Assemble the levers in the middle of the room and pull them to move to the
 actual cell block.  You can access any of the six cells for goodies, but the
 Princess is in the third one on the right.  Have two characters in there to
 step on the buttons to free her and finish this mission.