The two tanks in Halo 2 have different weaks spots (and strong points). The human Scorpion tank has a turret that is almost invincible; it's naturally vulnerable in the body and the four tread motors (which count against its hull integrity).

The alien Covenant Wraith has a very strong glacis (the front armored bulge where the pilot is). Consequently, it has a very weak rear.

Rockets affect both tanks as if the weakest facing is used, meaning two shots will knock out any tank.

Expended all your ammo at the end of one stage and don't have enough to muscle past the start of the next one? Save and quit your game -- provided you acutally unlocked a new stage on the Stage Select, you can head back into your campaign (via stage select) and get a fresh batch of pre-assigned weapons for Master Chief.

Co-op players already know from the first game that your partner and you can kill one another (one a time) to restart with an initial ammo load when you started the stage.

When you first get on Earth, go through the first opening into the courtyard. Head over to the right side where the buildings are. Follow the wall until you see an alleyway on your right. Enter it and follow it left. Stand on top of the pile of dirt at the end of the alley and while facing the wall, do a jump/crouch to get on top of the buildings on the block. You'll be able to clip the stage at the very top.

Attack rapidly with your melee by "switching weapons" as soon as the melee attack connects; press the Y button marginally before the B button (default button setting) to see your SPARTAN in action.

Ghost
rocket x1, gauss x1, grenade x1, sniper rifle x8

Spectre
rocket x1, gauss x2, grenade x2, shotgun x6 (close)

Warthog
rocket x1, gauss x2, grenade x2, shotgun x6 (close)

Wraith
rocket x2, gauss x3 (front), gauss x2 (back), grenade x13, tank shot x2

Scorpion
rocket x2, gauss x4 (body/tread), grenade x15, tank shot x2

Banshee
rocket x1, tank shot x1, shotgun x6, brute shot x4 (impact)