If you already have a company name, and it makes sense to use this company name for your new ecommerce site, go with a domain name that closely matches your company name.

If not, here are a few tips:

• Get a .com domain name if at all possible. It's believed that Google gives more weight to .com domain names so start their first.
• Avoid hyphens / dashes. These are more difficult to type, remember and explain to others.
• Choose a name that's relevant to your website. It should reflect what your core niche is, and make sense to your customers.
• If you're going for a highly targeted (long tail) niche, consider an Exact Match Domain (EMD). Despite Google's 2012 devaluing of EMD's, they're still proving to help with search engine results. So if you're targeting the silver disc sleds market, try to grab silverdiscsleds.com.
• Get creative! It's very hard to find just the right domain name. If you can't find exactly what you're looking for, be resourceful and look for domain names that are similar.
• Add a prefix or suffix, like (silverdiscsledshq.com or thesilverdiscsleds.com or silverdiscdepot.com).
• Consult a thesaurus for alternative words that still fit your needs.