Starter problem.

The starter worked fine earlier today. I was tuning the engine and stopped and started a couple of times when it gave in. First it would sound like it would not engage fully and make that rattling noise against the cogs, then it only clicked. I turned the engine by hand and tried again, the exakt same thing.
I have a fresh battery but tried another with no luck. Could it be a ground fault? Not too familiar with electrical issues, any suggestions on how to start ruling out faults?