Star Wars: Battlefront II/Heart of Darkness

Get to the AT-TE
There's not much to this objective, it gives you a yellow objective marker and everything. Just spawn as a normal soldier or rocket launcher and walk to the AT-TE. Walking, it takes 10-15 seconds to get there.

Kill 6 acklay
These things are nasty. They can kill you with one swipe of their pincers. So if you chose to use the grunt soldier, find one and start shooting it. Once you hit it a couple times, it will start charging at you. KEEP FIRING! Just back up and keeping unloading into its chest or neck. Repeat this procedure for the other 5 acklay. Note: there is a critical hit somewhere on the acklay, it is either its head or its front legs. If you find it, be sure to aim for that. Or course, if you chose to use the ARC trooper, just make sure you hit the acklay with your rocket. A way to do that: switch to your pistol and get the acklay to run at you. It isn't smart enough not to, so just wait until you can't miss and fire a rocket into its chest.

Defend the AT-TE
Your troops will do this pretty much on their own. If you want to switch to the normal trooper, go ahead, but a blaster pistol works just fine for this part. You shouldn't have much trouble taking out the few units that attack the AT-TE.

Acquire the power cell
Remember what was mentioned earlier about the word "acquire" in an objective? Well, here it is again. Take Aayla Secura and follow the yellow arrow marking the objective. Don't bother with any enemy units on your way to or from the downed LAAT. Just pick up the power cell and take it back to your base (again denoted with a yellow marker).

Destroy the CIS defense turrets
Unless you made a big mistake, you should still have Aayla Secura. Look for any turrets, marked by yellow arrows, and attack them with your melee attack (as opposed to the "throw lightsaber" option). There are 6 turrets in all; once you've destroyed them, the level will end.