Using a new domain for the same site...

ok my old domain is two words written together, i think it will do better if i seperate the two words with a dash right?

but the real question is...can i just like.....add the new domain so there are two domains pointing at the same site?
or do i need to remove the old domain before i get penalized or something?

dash is not a good idea
but if you want to use 2 domains, you should put the new one with 301 redirection code to the old domain

If you use two domains just be careful not to duplicate any content. At best the duplicated content will be ignored on the lower ranking site. At worst Google may consider it a copy site and it will just be ommitted from the SERPS.

Personally I'd steer clear of changing the whole lot to a new domain wiht a hypen in it. There's two reasons behind this...

1. Your site is established. This means that you'll be starting again right from the start which means no rankings, no PR, no visitors, etc. It's a big issue to worry about.

2. People that visit your site now might have it bookmarked, or try to remember the name as it stands. What happens when they can't find it any more? Lost visitors.

What I'd suggest as the best solution (which could easily be disagreed with) is to get the new domain with the hypen in it and have that domain redirect to the new domain. Don't have it as an "extra" domain that'll show the same site on the two different URL's though.

i found that only german domains (.DE) use a lot of hyphens in their domain names. (i am from germany)
have it redirect to your other page and you should be fine - i did this with a couple of domain names ... just because other names are more catchy and more ideal to advertise with in printed publications for example.