This question has been there not only for domain names. We always struggle when ever it comes to picking some thing a baby name, buying new cloths, new car so on and so forth. It’s the nature of human being we are never satisfied with one thought.
I would like to share a small guide on how to pick a domain name.

1. Define project

The first thing you should bear in mind, what should actually be found on the new site. In accordance with the content should be just the domain will be chosen.

2. Rules of thumb when choosing the domain

Keywords: Respect the fact that your main keyword is found in the domain. For example if your website is related to “online shoes” it would be better to get a domain name which includes that word or phrase (www.onlineshoes.com). From search engine optimization point of view this will make things easier for SERPs.
A domain registration with keywords in the URL gives you a decisive advantage.  Every time someone links to your site, while not using descriptive link text, but only the domain name is still linked with an important keyword on your site.

Let’s take the same example: Suppose your site deals with the topic of Online Shoes. A descriptive domain with keywords would e.g: www.onlineshoes.com
Every time someone link to your site and used the name of your domain as the link text that is linked with the keyword "online shoes".
This has the advantage that your web site on the keyword "Online Shoes" is considered relevant.