When you have the site up and running and you have already thought about a lot of other things; you need to find a way to bring visitors to your website.
There are various traffic building websites that you can use to get traffic to your website for free. It is like an exchange.
Traffic Syndicate is a very good traffic exchange. You surf a few sites and then you can place your website their to be surfed.
(I surf yours, you surf mine) kind of idea.
You need to spread the word; tell people, post on forums (Relevant posts), post a blog, email your mates (Do not SPAM!) and advertise on social networking websites.
The most important thing, is to make sure that your website looks good or trustworthy. This way, if people visit but do not buy something the first, second or third time; they might come back and bu something the forth time because they believe that your website is trustworthy and they feel secure making transactions through it.
Keeping People
Once you have people registered with you or who have bought one of your products/services, then you need to do your best to keep them.
The best way for this is offers, great support and overall politeness.