Hi Dale,
It is important to acknowledge people, have them see you as a person trying to build relationships and not just as one business up for the sale. Avoid promoting your company/ product directly, do not tweet "Bags for sale at low prices!", instead share one useful informational blog post link about your product. :) Keep your message desirable and relevant, Twitter is meant to be a social tool so do engage in conversations, thank re-tweets. :)
Provide the link to “Follow Me on Twitter†in your website, blogs, in your email signature and forum posts. :)
You can actually import your contacts from Hotmail, Gmail and from your own address book at Twitter.
If used correctly to provide positive exposure to your business, Twitter can be really be used as a powerful marketing platform. Nowadays companies make thousands of dollars of sales from customers who found them from Twitter.
:)