I would appreciate the infomation if anybody knows.

up on d-pad then press square i think

Hit up on the d-pad(brings up visor) then square to mark the enemy.

Okay how do you know when a player is tagged?

They'll be lit up red

You don't have to press square in multiplayer and it doesn't seems to work if the enemy is really far away.

It does work, but the moment you press, your crossair in the visor has to be ON the target. Unlike in the SP where you have to be around the target?

Tried to tag a couple people for the 30 spot assists, but my teammates don't kill them and I always end up killing them myself.

So press up on the d-pad then square to tag then your squad can see the player you tagged to?

Yup and if people kill the enemy you tagged, you get a spot assist. ( 30 spot assists and you get a trophy BTW )

The only crappy thing is, your crossair really has to be on the target when you press square...

i usually hold down the square button and i thought that's what you had to do. up on dpad then hold square over the enemies. perhaps i need only press the square when the crosshairs are right over the enemy, i'll check it out tonight. i think spotting is very cool, i spotted endlessly in bfbc2, and not used enough in c2. it can be devastating, especially if you are able to light up their whole team.

i usually hold down the square button and i thought that's what you had to do. up on dpad then hold square over the enemies. perhaps i need only press the square when the crosshairs are right over the enemy, i'll check it out tonight. i think spotting is very cool, i spotted endlessly in bfbc2, and not used enough in c2. it can be devastating, especially if you are able to light up their whole team.

It's really useful, more people should do it, if a tagged enemy goes into cloak he's still lit up in red + you get assists + points if the enemy dies.