You're wasting your time with it, unless you're mining in a pool or with a GPU you're basically just wasting electricity.
Hardly. While the odds of generating a winning block are low that extra few kH/s of computations has just added a little strength to the bitcoin infrastructure. Certainly not a complete waste.
if you look in your startup folder (windows) you should find the shortcut to bitcoin client. Add the command line to generate coins to the end of the command and It'll always run and generate.