Try and make your domain name as close to your company name as is possible if your company name is already well established outside the Internet. Many visitors may try to guess your domain name based on your company name (e.g. www.yourcompanyname.com), and by increasing the possibily of they finding it without having to resort to search engines, you can increase your traffic.
Try and register domain names with different extensions (e.g. .com and .co.uk). Particularly if you are aiming at a regional audience as well as a global one. If you are a UK based company then a .co.uk domain will give your UK based audience the confidence that they are dealing with a company 'close' to them as well as ensuring International audiences are aware of the fact that you are a UK based company, while a .com will ensure that you will attract casual visitors as much as provide your site with an International profile.
Use words in your domains which can be visualised. You want someone to remember your domains above all others and words like red, hot, etc. can prove to be more memorable than simpler names but there is the danger of over-doing it and names like easythis.com and easythat.com can become tedious - adding to a negative reflection of your site from the first visit.
The right domain names will help improve the profile of your brand and ensure you strengthen it on the Web. The wrong domain names can cause the reverse to happen. As you will probably be using your domain names for email as well as other marketing you will need to ensure that they are both memorable and enduring.
Registering a long domain name containing a list of relevant words for your web site may achieve a higher ranking in some search engines. Several of the major search engines rank web sites much higher if the search terms are contained in the domain name.