Here are few tips that can help you to get more Youtube Subscribers..
1. Give incentives.. Like for more benefits, please subscribe..
2. Advertise on other media. For example on Facebook and Twitter.. This definitely helps.
3. Some people forget that youtube is a social network as well. Interact with others.. Comment on others videos. Make use of social network, Youtube!
4. Use annotations - "subcribe for more" kind of annotations..
5. Bribery: Offer something.. For example, say "I will giveaway this or that ____" when I reach 2000 subscribers..
"I will play this prank___" or "I will do this dare" when I reach xxxx subscribers.
Hope you will like it.
The original source of article: Increase Your Free Youtube Subscribers count