#1
So I have been giving backup vocals a shot and I feel like I do pretty well for what it's worth. I find that I also keep time a little better. Are there any general tips, being that I'm pretty much brand new to any kind of singing while playing? Distance from the mic? Volume? EQ?
#2
Lots of practice, distance from the mic varies, but try not to get more than about 6 inches away most of the time. Volume should be slightly below lead vocal volume. EQ varies from one person to the next.

Here's a sample, recorded with the band I'm with now about 2 years ago. First time we had played together in about 15 years, no practice and I didn't warm up enough. You can hear a few places my voice is giving me trouble and one sour note in the first chorus. Shane and I have had a running but good natured argument going, I think I hit the sour note, he thinks he did. We decided to keep it against my better judgement, about 5 hours into the recording and that was the best track so far...should have redone it again though. Total was almost 8 hours making this one.

I did all the lead vocals and harmonies on the verses, we all did two takes of the choruses to get the choir effect. I did some of the high harmonies, Alan did some of them. I did two different parts in the choruses and I think Alan did too so we wound up with 5 parts I think it was.

This ain't great, but it gives you an idea what kind of balance you're looking for between lead and backup vocals, all 3 of us have different EQ. I'm having trouble with the high notes these days, I caught the flu and kept singing right up till new year's eve 20 years ago and had no voice at all, I think it scarred my vocal chords and I lost about 4 notes off the top of my range, which is why I have a hard time with the high notes now, and on that day I didn't take long enough to warm up. Never sing with a cold or flu...We did one practice run with just one acoustic and started recording.

https://www.youtube.com/watch?v=iKnqSKQCIs4

Anyway this is the kind of balance you would want to go for, harmony parts just slightly behind the lead. This was done with a condenser mic, different from the usual stage mic, you generally get a little further away, a foot or so... I'm the bearded guy...
Hmmm...I wonder what this button does...