Need help with my singing.?

I started practicing singing on my own about 3-4 months ago using some techniques I learned online. For example I have been trying to control my swallowing muscles by putting my fingers under my chin and trying to imagine the sound is coming from higher up in the mouth. I have noticed some improvement in my singing but I still want to get better.

What I really need help with is the diaphragm because I can't seem to find a good site that explains how to properly breathe while singing. Another thing that I need cleared up is how to use your tongue when you sing, because I know it is supposed to stay at the bottom of your mouth, but I find this very difficult.

Basically any general tips that a beginner singer could practice on a day to day basis would be greatly appreciated. Sorry this is so long!