Mine have been quite successful 
1) Research before making videos, The HH Forum is a great place to look!
2) DO NOT ASK SUB 4 SUB ~ It IS ANNOYING!!

3) Upload Regulary, People will unsubscribe if you do not upload regulary!
2 times a week is a good amount 
4) Comment nice things on other Peoples videos, there is no point in Disliking Videos and Commenting mean things, If you did not enjoy the video, Just click off! There is no need to waste your time disliking and being mean ~ It is not going to get you subscribers!
5) Maybe feature your Hamsters in your Video, 99% Of People would prefer watching your Hamster rather than a still Image of your Wall! 
6) Enjoy making Videos! No point in doing them if you do not enjoy! 
7) Reply to Comments! People spend time commenting on your videos ~ Reply back! Be kind and Open as they have viewed your video and taken the time to comment!
Those are some things that have worked well for lots of other people! For me, I use numbers 1) 2) 3) and 7) most and that has helped make me fairly successful on YouTube!
Hope this tips helped! :P :P
