Subdomains are best.Especially if you have a domain that is linked to subdomains eg cars is the domain and then cars accessories,cars news, cars auctions etc the subdomains.Alos best to use anchor text and links to and from all pages
There are many ways to market a small business on the web. You can buy banner ads, text links, or use PPC. However, the best way is to get listed in a bunch of portals. Portals and directories are like phone books, and they often provide a lot of traffic because they tend to rank high on Google.
This portal is giving away a free business card holder for lising your business (I got mine a few days ago in the mail). If you want to know about some other portals, just let me know.