Using YouTube to promote your band

We're all fairly old, having spent at least half our lives in a non-Internet world, but I'm well aware that the expectations of a band trying to promote its music should be tempered by the realities of how people consume music nowadays.  Even just hanging around this forum, I've learned a lot about how people discover music, and one of the primary means that I've seen is YouTube.  Youtube has become a place to share audio as much as video now.

My question to you all arises because of a message I received to my Youtube account.  Having uploaded a couple of new songs in the past week, it must have triggered some salesmen types to solicit my business to help me get my videos to "go viral".  It was actually a very nice message, going on for paragraphs about how amazing my uploads are, but it was pretty obviously a form letter.  I'm not that old and naive. 

How do you attract traffic to your band's music online?  What methods have worked?  What should I avoid?  Is this message I received worth investigating?  Should I just give up now before I die penniless and insane? 

I like your stuff on Bandcamp btw Andy... I hadn't checked it out in a while.

But your remark brings up another good point -- just what is our goal anyway?  That's probably a discussion we need to have.  I don't think we have any illusions about actually making a lot of money.  We just want people to like us, I guess, and maybe let us play a gig for money somewhere, every now and then.