Sony Vegas is a great tool for mixing, especially with video related projects. I've made this simple tutorial on it to show how to get the basics of it since I've known people around here can sometimes feel a bit overwhelmed when they first see the program as it's got a lot of options. Regardless of all those options however, it is quite an easy program to get the hang of.
(click on the images to see enlarged)
When you first open up the program you'll get the default layout which I find a bit much for most stuff that people do around here, so I suggest cleaning it up a bit before doing anything. I usually close the second and forth windows across the top, leaving us with only the Project Media, Preview and Timeline windows (you can do that by just clicking the x in the corner of each).
To make sure you don't lose this new layout, go up to view and hit "save layout" and then you can name it whatever you please. You can also go back to that same menu after saving to see that it's now listed in the custom Layout listing; so if you need to use a different layout sometime you will always have it to return to. You can also go to "organize layouts" in the same menu to delete any layouts you've made.
With the layout taken care of, it's time to start preparing the project for media. I'll first go to the media window and right-click the "Media Bins" folder and say "Create New Bin". This creates a new folder where the future media will be placed. I'll usually start off by naming it "Video", and then repeat for other instances (Audio, Music, ect).
After that has been set up, bringing the media into the project is pretty easy and will be well organized. Make sure you have the folder you want selected and then go to File > Import > Media. Choose the media you want and click okay. It will be inserted into the folder that you've selected.
Once there's media in the folder, you'll see it in the other area of the media window and can drag it on the timeline below. If it's the video, it will not only appear below on the timeline but it will also be shown in the preview window to the right. You can move around the slider on the timeline and that will scan through the video in the preview window.
After that you can continue to bring in media and move it around onto the timeline where you want or need it to be. Right-clicking the tracks below will allow you to add further video/audio tracks (vegas is pretty unlimited) so that you can have wide array to mix your audio, music and sfx on. Once you've gotten everything pretty much mixed then you can head off to the rendering. I'd suggest rending the project out as an audio only track and then putting it together in Virtual Dub as that tends to help keep the file size smaller. However, you can play around with the settings Vegas has as well if you wish to see if you can get something good from it.
Extra useful features
You should have the Normal Edit Tool already selected. It can move files around on the timeline as well as trim them down (if needed) by clicking the edge of them and dragging it.
To Zoom in you can hit the Zoom Edit Tool at the top which is good to get closer if you can't quite tell where to place something.
So that's pretty much it for the basics.