Hows Can Descritions Be Improved To Rank Videos Higher?

I changed tags in 12 videos and 2 got in to extra 200 playlists. They are popular before but dropped to 40 playlist each. After update 240 each. I did not update tags before too. Now I am thinking to do it every 2-3 month. I do not know how long it takes to get new tags effective in the YT search and can't find any information about it.[DOUBLEPOST=1468329968,1468329915][/DOUBLEPOST]
I will check it out.

How do you know how many playlists the videos are in??
The biggest thing I've done it the past for video descriptions is have each of the videos as a Scheduled Upload with part of the video description as automatic default section and then add all the unique and customized stuff about that video at the beginning of it. Even writing this stuff up in Google Doc and organizing some of your written stuff for your content on Google Drive has helped out a lot. So that might be helpful in organizing material. :)
Include the title in the first couple sentences of the description. Include as many keywords as you can while still making it sound natural. Again, this is most important in the first couple sentences (not sure how many characters exactly). Make sure your title, description, and tags contain plenty matching words. I believe youtube's Creator Academy has a course on this which has some good info.
just came from visiting your channel, SeanFace101, wondering why you do not post videos at regular intervals, you skip a couple weeks, then you post 4 in one week, why don't you use the schedule feature to give your subscribers a steady stream of content on which they can rely?
Yeah I kinda thought about that too, that's my videos are uploaded sort of randomly :p Iv never scheduled a video to upload before, not sure if I know how to doo it lol. :p
Ill have a look and give it a go from my next video upload onwards. :D Thanks .P
The great thing about Scheduled Uploads is you can produce a bunch of content ahead of time in a 1 to 3 days and then publish it over the next 3 or 4 weeks depending on how often you upload.

It will reduce the pressure and stress to upload all the time. Just have to keep it up and it opens the possibility of time sensitive content too.