Want to know which domain name we have to choose so here is the answer mine suggestion is that you have to choose as shot as small domain name which will be remembered by the users who visits our website and the domain name also has to be the keyword based on the website content it will help every one to get ranking in search engines.
I know keyword based domains are great. But a lot of keywords are simply gone especially the .coms. So I presume its ok to use other letters or words with a good keyword. This is better than using "-"'s (hyphens) or numbers or anything else. .orgs and .nets are selling well as created websites I've heard. Correct me if I'm wrong but keyword + another word such as "world" or "page" or "site" or "academy" or "muse".
I think a domain name should be chosen on how you intend to use it. Small names are good for branding and remembrance though they contain no keywords. The keyword domains help with the organic search traffic. Branding buy-tools-to-make-money.com may be impossible and may look a little too spammy for people to click on in a search even if it did well in the SERPs.