what's the best way to promote a new online business?

[Tony]

Facebook, MySpace, and such sites are tools that can be used effectively to gain more traffic to your own site if you learn to use them properly.

However, before you get started, I highly recommend coming up with an online marketing plan and sticking to it.

To create a basic plan, you might want to answer the following questions:

1. What words are people using to look for your products?

This should influence your choice of a domain name unless your store is already so large that a lot of people search for it by name in the major search engines.

2. What domain name are you going to use?

A good domain name will include a strong keyword phrase that people use when searching for the types of products you offer. Ideally, the phrase(s) used would have relatively low competition and high search volumes.

3. How are you going to get people to find your site, specifically?

There are a huge variety of options, each of which works when properly understood and used. In addition to social networking sites like MySpace and Facebook, you might want to look into:
* Directory Submissions
* Creating an xml site map
* Creating an rss feed
* Using feed aggregators
* Writing articles related to your products and putting them on your site.
* Using Squidoo, Hubpages, Wetpaint, and other such sites
* Using Twitter and Social Bookmarking sites
* Joining forums related to the products you offer

The main thing that MySpace and Facebook offer which a new site does not have is traffic, though targeting that traffic well can take some doing, especially if you are new to such things.

Rather than jumping in and trying things, you will almost always be better served by creating a plan and sticking to it. Of course, a plan requires researching your options...but it sounds like you are doing that.