Mic Sweet Spots

Is there particular proven process for finding the sweet spot on your cab for the mic? I have a Shure SM58 and I just want to know.

Are there places that generally work better than others is there something I should be looking for, looking out for, distance?

I am a complete newby to the mic thing and am excited to finally be able to mic my amp rather than just plug into my comp, which sounds like shyte.

So any help in this area would be most appreciated.

Put it in the center of the speaker and move out to the side until you find it.
Place mic right on the Cab.
If your budget allows get a second mic to put somewhere else in the room for ambience.
I would suggest to walk around while playing until you hear the sweet spot in the room for sound/ambience and put the second mic there.

Tim's advice is good. I would suggest getting some isolation headphones and listening to what the microphone is picking up. You can move the mic around and find a tone that suits you best.

It has all been said, experiment, center is bright towards edge is warmer. One good thing to do is once you have found the sweet spot you like, put tape on your cab or mark that spot somehow to remember it.