Manual mode is for those who understand it. If you dont know what the needle means, thats beack to first grade to you, buddy - read the manual, read the web, and learn what exposure is. Dont bother with M until you have played with Av and Tv and exposure compensation. Setting all the controls until the needle is in the middle is nothing more than doind the built-in lightmetes's job, and doing it mechanically. Its the last thing you should do.
Use M mode with:
-flash photography (where you set a static exposure and let the auto flash do the job), dont care about the needle
-handheld lightmeters (when you use a more expensive and precise lightmeter, and enter the data indicated in your camera, and dont care about the needle
-pano pics (where you select an exposure in Av or Tv then set it in manual, so the exposure doesnt change when you move the camera), dont care about the needle
-etc...
As you see, in M mode the needle is only there to give a very small assistance. The whole idea is not to use it. If you use it, go to Av.