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.