Take roots that work best at the end of the names and enter them into column two. Then combine each root in the first column with each root in the second, writing down the new names that you prefer. If you need help coming up with additional roots or short word ideas, you may want to get a good crossword puzzle dictionary. There are also a variety of software tools available. In terms of software, there are some excellent tools for developing real word names as well as for facilitating your own brainstorming process.
Many libraries have reference books that list the most common ones.
In general, short real words are almost always already registered unless they are very unusual. If you want to use real words, try 2 or 3 short ones in combination, such as, funtogo. Remember that domain names are like license plates. Changing only a single letter is all that is often required to make an unregistrable name registrable. Remember that the only special character that can be used in a domain name is a hyphen.