Help on domain name suggestions on specific niche

I am planning to start a website related to technology and/or online learning tutorials with video/text. I mainly focus on what I know perfectly, like tutorials on wordpress, ms-office, oracle, java, seo, photoshop and etc.

I don't know the most searched keyword phrases on this niche. Please help me how to chose the domain name on this niche or guide me to how to find most searched keywords on this niche.

And does domain length also matters? if yes, upto how many characters, I may consider?

Thank you.

I will do the best i can to help you on this, you can contact me on Skype if you need/want to know more: f_rags_

Here goes:
Of course a killer domain that perfectly describes your business and has Huge amount of monthly search volume will cost you Thousands, however assuming you dont have a $50,000-$200,000 budget for a really good domain,
I would suggest you to go find an available for reg fee or ($100-$200) domain that includes a word that describes what you do and prefix it with (something you think sounds nice-see below for examples.) (Whatever you think will make a good brand if you spend time branding it)

If your plan is to get BIG, you could also go for a made up brandable name from the start and Focus on Branding Only the made up part.
Examples: (I dont own any of these, and they are prob all taken) Its just an example.

Dilex
Abria
Rilux
Stempex
Avora
etc etc...