Well I have made and edited a video (very long stressful method involving flash screen recording etc.) anyway I have my video with out-of-sync audoi so I open it in Sony Vegas 6.0 and re-sync the audio and save it in best quality.
The only problem is that once saved the quality is CONSIDERABLY worse than what I started with. I have tried everything. Am I doing something wrong. Please help me.
Thanks 
I use an earlier version of the sony software and I've never encountered that problem as far as I can tell. Did you output in the same format with the same settings (resolution, framerate)? Is the captured video digital or analogue?
It sounds like you are compressing an already compressed video format. When you do that, you will definitely see a worse quality.
What are the steps that bring you up to Vegas Video?
Well when you are making your video you are probably either compressing it again (like the person above me said) or encoding it with something. I suggest you look at your export options again. You have to have some way of making really lossless quality.
How is the quality worse? Can you describe it a lil more specifically?
Hey Dougie1 im guessing you tried exporting your video using all types of formats...but have you checked that your projects video settings are as high as your original video? If they are not then they will obviously be degraded somwehat.. hope that helps 
If you have already compressed the footage you're working with, you need to compress it in the exact same settings as you did last time. This way, the clip should maintain the good quality of the previous one. It may not work, but it has a few times for me.