As someone above mentioned.
Reddit - One of the best places to get new subscribers, it can be difficult if you're in a very particular niche but there's alway some subreddit most videos can fit in.
FaceBook - Search any groups related to your niche and post your videos.
Stumbleupon - A great website that will get you views and the off subscriber.
If you aren't get subscribers then ask yourself are you putting out the right videos for your audience, if people are watching your videos but aren't subscribing then you have to ask yourself, are you putting out content people want to see?
The very last thing is patience.... honestly, it's a long, hard, drawn out game this.
You're on this website, that's a start, now you just need to be consistent and patient.
Post videos daily, we all get burnt out, to prevent this make as many videos as you can in one sitting but schedule them to release on other days, aim to have one video per day if you can.
If you can't think of video ideas that's fine change your goal to having one really good quality video out per week.
Just hang in there, what you have to remember these big YouTuber's the one's who own channels you look up to or aspire to be, they all started out at 0. They all had a daily struggle to begin with, it's about patience and consistency, those who give up early on wont make it, those who stick in there and keep posting videos regardless will come out on top.
I post my videos because I am passionate about the topic I vlog about, I don't care about getting millions of subs, sure it would be nice but it's not my main goal.
Again, making money, would be nice but not my main goal. My main goal is to post videos that I'm passionate about.
If you love what you do and are passionate about it subs will come eventually.
It only takes one video to go viral or really make it before subs come rolling in. You just gotta stick in there and be patient.
Good luck and keep at it!