[Josh Schmid] “Is there a type of “template” or a trick I don’t know about?”
It sounds like you don’t know about Normalization which will bring your video levels up so that the loudest sound is at 0 dbFS and all other sounds will be raise by the same amount. To use it, right-click on an audio event and select Switches | Normalize. That should fix your problem with audio being too low. Of course the real fix is to record your audio louder to begin with.
[Josh Schmid] “Is it better to edit audio through speakers or headphones?”
Headphones are great for picking up subtle problems like lip smack, breathing, background noise, etc. but I would do your final mix using speakers. You still need to use the meters built into Vegas Pro to judge your overall volume.
[Josh Schmid] “Is it bad if the audio hits the top of the Master bus?”
Yes, it’s very, very, very BAD! Unlike analog tape which gracefully saturates, digital audio clips. It’s simply throws away the data above 0dBFS which clips the tops off of the waveform and sounds absolutely horrible.
What you want to do is place a brick wall limiter like the one in the Wave Hammer Surround plug-in on the Master Audio Bus, select the Volume Maximizer tab and set the Output Level to a safe level like -3.0dB like the image below:

That should get your levels under control. Then you can learn about using the Track Compressor (which is on every track by default) to further refine the audio levels. I would start with the “[Sys] 2:1 compression starting at -18 dB” preset to keep things under control at the track level.
What you need to understand about audio is that it’s additive and non-linear. Which means that if you have one audio track at -20 dB and you add another audio track at -20 dB your over volume will NOT be -20 dB because the two audio sources will be added together, but they will be added in a non-linear fashion. When you double the output in audio it only raises the volume by 6 dB. So two audio tracks at -20 dB will sum together for an overall volume of -14 dB (which is 6 dB louder).
What this means is that you can’t just set all of your audio tracks to -3 dB and expect the overall output to be -3 dB, It just doesn’t work that way. You have to set the lower so that they sum to -3 dB. That’s why I recommend using Wave Hammer on the Master Audio Bus to keep things under control.
Don’t worry if you don’t understand all of this. Just let the plug-ins help you keep thing under control.
~jr
http://www.johnrofrano.com
http://www.vasst.com