Here are a couple of tools that will help you choose and register a domain name:
domain naming tipps: A list of things to consider when choosing a domain name.
domain name suggestions generator: In case you need a good domain name idea this tool will generate a list of possible domain names on the basis of keywords provided by you and check if they are available.
compare domain name prices: Compare the prices of the top domain name registrars and filter it by price, top level domain, available payment methods and by whether or not anonymous domain name registration is possible. This will help you find the best domain name registrar for you.
domain name availability check: Test if your desired domain name is available.