Star Wars: Battlefront II/A Line in the Sand

Hold the Beach Command Post for 3 minutes
This is debatedly the hardest objective in this level. "Beach Command Post" refers to the forward command post on the beach; the timer will start once you capture it. Then you have 20-30 seconds before the CIS assault. They will throw everything they've got at you, so be prepared to defend against a horde of enemies. Don't bother using an Assault Trooper to destroy the Snail Tanks, your allies will focus their fire on them. You need to make sure that a minimum number of enemy units make it onto the beach. This is a long 3 minutes, and if you lose the command post, the level will be aborted.

Fall back to the Wookiee base
There's no definitive reason why this is even an objective. All you have to do is run back behind the shield wall.

Defend the Oil Refinery for 4 minutes
This can be tricky, but not if you know how to do it. Jump into an IFT-X and sit in clear view of the main entrance to the area. Use both your primary and secondary weaponry to demolish any enemy units that attack. This is a suicide mission, no doubt, and you will be destroyed. The timing of this fate, however, relies on your skill in the game. Remember that you have infinite ammo in both weapons, so don't hesitate to give them everything you've got.

Take over all CIS Command Posts
Yoda is available with this objective, so unless you are Dagobaphobic, use his powers to your advantage. Take the command posts in order according to distance from the Refinery. So take both on the beach in front of you, then move up the beach to the auxiliary command post (look out for units hiding behind the rocks). If you still have Yoda, great! Just keep steamrolling everybody and take their last command post. If not, don't worry about it; use a normal soldier and drive another IFT-X, this time straight into the middle of enemy territory. Clear out the enemy units guarding it, then get out of the tank to begin capturing the CP. There's a good chance you'll become the receiving end of a Snail Tank's grenades. Don't worry, you should have enough units available that you can respawn at the nearest CP. The only thing you absolutely should NOT do is try to kill units without taking the command post; the enemy has no reinforcement limit, so this won't do any good. Once you capture the last CP, a cutscene will play.