On Bespin Cloud City, I always take the upper passageways first. Don't even bother with the courtyard. Once you have taken the upper passegeways, then you can fire down on the courtyard. Lots of enemies will be in the turrets making them easy kills. Once you have the passegeways secure, go ahead and take the rest of the command posts. Leave the courtyard for last because the enemy has a disadvantage there.
Same idea with Yavin 4 Arena. Take the two higher command posts. Don't worry about the middle command post until you have both turrets and a bunch of snipers firing down and backing you up. Then take the outside command posts.