Tips for reducing rendering time?

Really also depends on the software you are using, if you do rendering often it is probably worth buying a good rendering software.

Try to avoid photorealistic animations, I find they slow down the rendering quite a bit.

Turn off the lights! Well not all of them of course but just the one you don't really need. Lights normally take quite a bit of time.

Autodesk has a rendering tool called the cloud that produces extremely nice renders. You do need to have a account for it though, but its worth because once you start the render you can go back to immediately working on your project while cloud renders in the background.