I'm looking at upgrading from my low quality shotgun mic to some lav mics, so I can be sure to capture consistent quality dialogue. Any suggestions from more expreinced sound people?
Lavs can be much more trouble than they're worth if you don't have much experience.
Probably the most common error is mic placement, and the second most common is mic selection. These are the two things that matter most.
Get the mic off the top of your camera. Put it on a boom pole and get it as close as you can without dipping into the picture. Placement is huge, and the closer you are the more of the direct sound you record in relation to the sound of the room (reflections, background sounds). You're also gonna get a better recording level. When you have to raise the volume of a low-level recording in post, especially if you're using in-cam sound that pretty much sucks, you're amplifying self noise from terrible pre-amps.
Booming the mic also allows the mic to move to follow dialog, and it allows the mic to point at the people instead of at the wall or straight toward the background so that you aren't recording as much of the acoustic crap that tends to get in the way.
Shotgun mics are great in lots of situations, but they have a weak spot. I could bore you with lots of tech-speak about interference tubes, phase cancellation, and comb filtering, but the simple version is that the thing that makes shotguns really good at rejecting sounds to the sides and rear, is the same thing that makes them terrible in really echoey rooms. For those situations, a hypercardioid (small diaphragm condenser) can sound more natural.
The other thing that may help, not knowing which camera you use, is to record sound separately - to a dedicated sound recorder - and match it to the video in post. A dedicated sound recorder does just that: it records sound. You'll get better quality all around.
