if you want to do it yourself, check the secretary of state website, usu. there should be a tab called BUSINESS or CORPORATION, go in there, do a search on your intended name, if there is an overlapped name, system will show..
for federal registration of trademark (to make sure that your com. name does not infringe on other's trademark), go to USPTO's website (www.uspto.gov, i think), click on TRADEMARKS or SEARCH TRADEMARKS tab, type in your intended name, if there is anything similar, will pop up..
hope this helps.