Here's the thing, if you aren't shelling out money for a TV ad there isn't any place to just promote your stuff without ticking people off. You have to become a part of things to be good a promoting your stuff. You have to hang out where your viewers hang out and get to know them, gain their trust by becoming a part of their community.
This works because I do it at cooking blogs, forums, and websites. Everyone just wants to "promote" which I see as "spam video dropping" the kind of stuff we sometimes get in the intro area. "watch my video" "check out my channel." No one likes that.
It's OK to do on twitter every once in a while, and Facebook (especially a your fan page). However, they will eat you up on Reddit for that. I get viewers from the forums, sites, and places I visit without ever asking anyone to check it out. Once I've been a part of the community for awhile regulars eventually click my name that leads to my YouTube channel. Yes, this takes time but it's worth it. You might even learn something and make some connections.
Some promotion ideas off the top of my head:
- Tweet out upcoming events, but make sure you tweet about other stuff or tips, announce giveaways but tell them what it is until they come watch a video (tease), etc
- Become a valuable member of blogs where your name is linkable to your YouTube channel
- Start a blog with valuable information and promote from your blog as much as you want
- Go old school and local by handing out cards/flyers at local video gaming events
- Always wear a Tshirt with your YouTube channel and logo, on the back
- Start a Facebook Fan page
- And the all time classic, try and collaborate with your peers
That's all I got for now, good luck with your promotion.