"I tried a lot of different methods of advertisements and promoting, only two of them really worked out for me. When I used reddit I got a troll, when I tried twitter I got lots of followers but only 1 subscriber, when I tried adword I spent 17$ on promoting my channel trailer to guess what... get no subscribers at all.
One method that worked pretty well for me was to just go to a large content creator's video that is in a similar field as yours and to leave comments on their videos. Do not self-promote on their videos leave meaningful feedback or a relevant comment to the video portrayed. Most of the time if people like your comment it will boost up to the top of the comment list, which leaves people a click away from going to your channel. I actually have a ton of +1's on google+ because of how good the comments I leave on peoples videos are.
The second method I used takes a lot more work (A TON MORE WORK). It was just to email people who seemed to enjoy the type of content you are creating. I made a pre-made message and went to a popular YouTubers video's comment section and clicked on each person individually sending them a email. The email I sent them just asked for feedback on my channel and nothing more, I didn't ask them to subscribe or to even like my content just for feedback (the feedback has helped me out a lot). I have sent over 2k emails out using my memory to try and not send duplicate emails out to an individual. Some of my subscribers came from this method and the ones that did come from this method are much more talkative than the latter. It does take a long time to send out this many emails though.
So yeah those are the two methods that I have been doing, and only those two methods recently. I tried many other methods and none of them seem to work for me. The first method is how I got to 100 subscribers and I didn't even use the second method until after I passed 100 subscribers. Anyways I hope that helps you out a bit!"