[STCrowley]

My advice is to use the simple past when you're not sure. It's not always right, but it's the most common form of the past.

For the past perfect ("I had driven a car") we use that when comparing two time forms. I tell my students it's the 'more past.' ("I had driven a car before I got my license.") It emphasizes that the 'had driven' is earlier--as far as time--than the getting.

As far as the present goes: I suggest you use the present perfect (I have driven) when you talk about first times, but normally we use the simple present (I drive) or the present progressive (I am driving) when we talk about things that are happening now.

The difference here is that the simple present (I drive a car) means only that it's something I do in general: I'm a car driver. The present progressive (I am driving) means that it's something I'm doing at this moment, right now. (It doesn't mean that I normally drive, though.)

I hope that helps. If you have more questions, feel free to ask!