Whenever you upload the video on YouTube, ensure you create a KILLER THUMBNAIL image with text. Add a proper and detailed description with previous video URL links, Twitter profile link, Google+ link, Facebook follow links, WhatsApp chat number.
I upload tutorial videos like bypassing Lock screen and how TOS. if they are unable to get through or unsuccessful then they will directly follow you on twitter or contact you on WhatsApp.
Connect you Twitter bootstrap and allow automatic share whenever you upload videos. Most of the subscribers, and viewers comes from out side YouTube so you need to be active in social medias like twitter and Google+.
You can also try alternative methods like Traffup, AddMeFast, and etc sites that offers free subscribers on the go by exchanging them.
Hackers never learns but always wins!