How to get decent Video footage ?

Don't just use footage shot from the boat. Experiment with shots from a stationary tube, a towed tube, another boat, even from the beach.

Be aware of where the sun is and how it is hitting your rider/subject. Proper lighting is ESSENTIAL!

If you're using a digital camcorder, more than likely it will have Firewire, which GREATLY simplifies editing. I have no experience with Vegas Video (I only use Macs) so I can't really comment on it. Look into Final Cut Express. It's only $250 and does everything you'll ever need if you're shooting DV (the color correction alone is worth the price of admission, especially considering how hard it can be to get consistent shots on the water). Step up to Final Cut Pro only if you're shooting higher resolution formats.

Remember what Troy and Ryan said in their posts, it's a lot of fun and really lets you show some creativity. That's what videography and wakeboarding are all about!