Always be in a happy mood and make good quality videos!
Dont record when your tired or sick just to be recording wait till your back to 100%
Have fun! That's the one thing that's has helped me and also watch a lot of videos on what you need! The most important is have a motivation my motivation is jacksepticeye and he make me go on through rough times in YouTube!
Shamelessly self promote at school or work. That is how I got 30 subs within 2 weeks which so far has been my best growth period.
Have a good upload schedule, interact with your subscribers, upload only quality content, honestly thats the only way.
Dont give up, be perssistant, do your best. If you put effort in there, naturally people will. SHOULD, notice it and therefor like it!.
Also, concerning happy part...no one can always be happy, sadly sometimes you force yourself to be happy for sake of it. But being happy constantly, 24/7 somehow i doubt thats doable.
Don't have horrible 3D intros and you'll have guaranteed growth.
I just say have FUN! I mean that's what i've been doing and now I started to stand while playing games! Can't sit down lol!
The tip is to entertain your audience