I was wondering, do you usa a single power supply or do you use 2 or more power supplys on the bigger tracks.

If you're talking wall-warts (power packs), it's best to have one per lane. If you mean one of the good power supplies, like the ones Alan Galinko sells, then one of those will do.

If you're making a larger layout, you will want to have some jumper relays to prevent power loss. Go to http://www.hoslotcarracing.com (http://www.hoslotcarracing.com/) , and click the 'power' link. It'll show you wiring diagrams, and power requirements.

I use one wall wart per lane. It seems to do the job just fine. It makes use of what I already have and will do until I can get around to upgrading.

On larger tracks, I've read that some people run power wires to the rails every few feet or so, depending on how big the track is and how many joints there are. You loose power where the rails on the individual pieces of track meet each other. I have also heard that some people solder the rails together at each joint. I suppose that would only be practical if you were setting up a permanent layout.