So you own a single website, and you have several domains. You want to make sure that even if your customers misspell your domain name they would still be able to get to your website. There are some important considerations surrounding multiple domain names routing to a single site and search engine submissions.
Most domain registrars offer the domain forwarding feature. You should however be careful. While it may be the easiest way to forward your domain name, this can cause some real problems when search engines spider your site.
The search engine spider pulls your domain name usually from a whois data base. The spider visits your website, using the domain forwarding through your domain registrar. Your domain registrar is using a Temporary 302 Redirect (Most likely because it's assumed that you'll point the domain name to a new hosting account sooner or later), frames, or other incorrect forwarding method.
The spiders index your site!
So, your domain registrar did its job, and sent the spider to your actual site when it visited the domain name you registered. The spider did its job and read the content of the page or pages it found and then incorporated them into the search engine index.
When the search engine spider read your page. It then associated it with your alternate domain name. The one that was supposed to forward you're domain name. This means that the search engine has effectively tracked down what it will quickly identify as a duplicate website. This can cause your website to look like spam or bad website. Thus effecting your how search engines see your website.
You domain names need to be routed from the domain registrar to a hosting account. Some registers offer domain forwarding using a 302 or 301 redirect. You'll need to set a Permanent 310 Redirect to your main website. A Permanent Redirect is logged as a code 301 (It's often referred to as a 301 Permanent Redirect). If you have multiple domain names you wish to direct to a single site this can come in handy. By creating a 301 Permanent Redirect when the spiders crawl you web page they will know that you really only have one website. This is acceptable to search engines and won't get you banned.
I could register the a (.com .net .org .info ext...) to protect my branding. I could also redirect these domains to my main website. Google is a great example, type in any extension you will be directed to their website.
One clever way to make sure your customers find you is by using your company name as your domain name. However, this can cause you to miss out on the advantages of a keyword based domain name. One way to take advantage of both of these is by using your keyword based domain name as your website name and using a 310 redirect on your company name.