Advice for shooting cars?

I've always liked cars, and I'm starting to appreciate photography more and more.

Can you give me some tips on combining the two hobbies?

Are there particular angles I should use/avoid?

Is bright sunlight better to make the car shine, or more diffuse cloudy day to avoid glare?

Other thoughts?

(Camera is an Oly E-P3, if you care, or if it even matters for the sake of this question.)