Saren

Saren on Virmire
Your first fight with Saren Arterius will take place on Virmire. In this encounter Saren will fight while standing on a special hovercraft. He will use powerful biotic attacks in addition to his weapons.

Tactics

 * Order your squadmates to attack Saren aggressively because Saren usually focuses on Shepard and leaves the remaining squad members alone.
 * Saren will often choose to hover over one of the many fuel tanks in the battle area. Shoot the fuel tanks (or better yet, Sabotage them) to take him out quickly.
 * Saren will continuously use his Biotics to damage Shepard from a distance.
 * Saren is immune to biotic attacks except for Warp and Stasis.
 * Saren can use his platform to distance himself from Shepard.
 * Use Sabotage to quiet Saren's weapons and Damping to prevent his ability-use as often as possible.

Saren on the Citadel
Shepard encounters Saren once again on the Citadel in the final moments of the struggle. Initially Saren rides his hovercraft once again, but once Shepard kills him (or convinces him to kill himself), Sovereign reanimates him in a new form. By controlling Saren's corpse and speaking in his voice, Sovereign has the turian fight one last battle. This second avatar of Saren/Sovereign uses tech powers rather than biotics and turns out to be quite a bit more powerful and dangerous than the original.

Tactics

 * Start moving as soon as the battle begins, and stay as mobile as possible because this battle is more about mobility than cover. There is cover available behind the big rocks at the front if needed, but if you depend heavily on it the battle will take quite a while.
 * This reincarnation of Saren is much like a Geth Hopper and jumps around frequently. Powers like Throw and Lift are a great help because they can keep him off balance allowing you to pepper it with bullets.
 * Lift provides the longest "stun", and should be applied wherever possible.
 * Throw provides a shorter stun.
 * Saren is immune to Neural Shock and Singularity.
 * Stasis will lock him in place once his shields are down for an extremely easy, if cheesy, kill.
 * Damping will prevent your weapons from being overheated by Saren's Sabotage.
 * Sabotage will stop the "fireball mode".
 * Once Saren's shield is down Warp can increase the damage your weapons do.
 * Again, keeping moving is your best defense -- you will take very little damage if you keep moving.
 * After you reduce his shields to 25%, the cut scene in the middle of the battle activates. Saren/Sovereign then regains his shields.