making the camera track an object

I want to make some kind of a sidescroller game, and I want the camera to track the character on a 2D plane (this means the camera must not rotate or move from the original plane, and it can move on its X and Z axis only.
How do I do this?
I’ve already tried the camera actuator, but it’s not ok for what I want to make.

make the main character a vertex parent of the camera (so you wont get rotation).
If you want some delay on camera motion you can use an empty slow parent.

camera -(slow parent)–> empty -(vertex parent)–> mainCharacter

…While there can be some glitches with this, I found in general it can work quite well.