Hi I am trying to make a video of a concert I shot. When i render it, the file is too large to burn on one DVD. I'm quite green when it comes to sony vegas and i was wondering how do i reduce the quality, so it can burn on one dvd (4.7 GB) large. the file size of the video is roughly 4.9 GB as said on the file, if that helps

Ideally you would use a bitrate calculator to determine the proper bitrate based on the length of the program.
Check out Vol. 1 Issue #7 of Edward Troxel's newsletters (http://www.jetdv.com/vegas/forum/viewforum.php?f=5&sid=baff516c2bc40ed07bd5cb31993a7afc).
He goes into some detail about the steps involved in authoring a DVD and includes a chart to help you determine the proper bitrate (as well as how to configure these settings).
Here's a link (http://www.johncline.com/bitcalc110.zip) to the bitrate calculator I use.
Note that this links to a zipped file.

Or you could output to a Dual Layer DVD, your choice...

This works for me:

http://dvd-hq.info/bitrate_calculator.php

Thanks for all the help, the article was a huge help to get things figured out