What I mean by this is this, I have a site that's few months old and would like to use a more brandable domain, however, I don't want to scrap the current domain because its relatively established. I would like the site to be indexed under bothe domains. is this possible or can it harm the existing domain?
No, making another site is not an option in this regard. Creating a new domain for an existing site and redirecting will not hurt the existing domain and its traffic, willl it?
But which domain will be indexed. The thing is, i wanted to do it for the purpose of boosting serch engine traffic as well by incorportaing a more global domain.
You will only hurt search engine rankings with the site on two domains. The only way to do it is to 301 redirect one to the other. Duplicate content hurts SERPs in all major search engines.
A 301 redirect will send traffic, including search engine bots permanantly to the other domain. This would transfer all the accumulated Search Engine value such as PR to the pointed to site, and the search engines will begin to send the traffic there directly and list it in the indexes (takes a while to work through the system). Moniker offers 301 redirects, most registrars only have 302 (temporary) redirects which are not as good. There is another way to do this in a file on your server. If you want to be indexed for both names then put good, non-duplicating content on each, then have links on one direct to the other. For example, have a site that talks about domains and lots of links on that site to another that sells them, and explains how to set up a website. You could get both well indexed. ---Some people believe cross-linking is bad SEO, I would have the links going only one way, if you need to refer to the other site you can give the URL without making it a link.
Yes a 301 is the way to go from the old name to the new, in theory page rank, seo rankings etc should not change but in practice it doesn't always work that smoothly. Just make sure you do it when it will have the least impact on your site.. Now is a good time if you sell products since the holiday rush has mostly finished.
doing a 301 redirect will tell search engine robots to treat the to domain as one. if you don't do redirect, google will index both domain as seperate site and maybe be penalized later