When you have a power up like rage or rally, and you don't want to wait for it to recharge, go to a command post and click to change equipment then press Circle. When it closes, you should see that your power up has fully recharged. You can keep doing this until you get bored or the game is over. Remember to make sure you have two doses of that power up. One to use and a spare when it wears off.
(supplied by: darkbot298)
On the place with the Sith tomb, jetpack over the big flames and you will turn invisible.
(supplied by: 4rb1t3r)