If you're answering any questions in your videos that are commonly asked, the initial question can be a good one. I make educational videos, so I usually answer a few commonly asked questions or something relating to that. Also, what you include in your description is very important, too. Include your sources and maybe even the name of the article so people are more likely to find you if that's something they're looking for. Google Trends is your friend!
I always search for the same topic and see what shows up.

my video is about film photography
I would search film and see what pops up
then photography and see what pops up
then take the best keywords from each search and include them in my tags!
Your channel name should always be included so you turn up in the search if someone searches for you. I've found Google's Keyword Planner helpful for coming up with keywords. By entering a topic or in my case a game title it will give keyword suggestions. You can see how competitive each suggestion is as well as average monthly searches for that keyword.
thank you ill give it a try mate
Lately I started to serious dig all of my time for improving the SEO knowledge because it's really important. For every video (having a LP channel) I check the name of the game and I see all the automatic suggestions (also typing the name and then a, then b and so on for the entire alphabet), helping my choices with google keyword planner and checking the monthly searches.
Everything double checked with tubebuddy: for every keyword I check the rating and if it's good or very good (of course with more search volume than competition) I use them. The problem is that even trying hard the results are not exactly what I expect, but it's because other aspects taken in consideration by youtube are watch time and audience retention....
think of words to describe your video. Like if you yourself had to search for it without using the title, how could you find it?. Funny, parody, etc.
ok thats a cool way thank you[DOUBLEPOST=1463503113,1463503017][/DOUBLEPOST]
So for different videos, I use different tags. For the long hair videos, it's a lot of "long hair for men" "long hair for guys" "guys long hair" "how to grow long hair" "how fast does hair grow" etc. It gets repetitive, but I make informational videos on that subject, so I want to cover any questions that people have (as long as the video covers that topic) in whatever way they may ask it.

For the puppet videos, I always use "puppet" "puppets" "puppetry" "puppeteer" etc., because those are fairly unique terms in YouTube, so they're easy to show up fairly high on lists. Of course, the really high-ranking puppet videos are for little kids, so I'm still not big on any really important searches, but I figure it'll catch on.
thats a good way thank you