When should we register a trademark?

Trademarks can and should be registered when when your mark is actually used in interstate commerce. As the first attorney to comment noted, an ITU can be filed and periodically renewed to place hold your mark. Before you beta test the branding however, have an attorney take a quick look at/research the proposed brand name to help you to determine the International Classification category(ies) in which to file and to make sure that the proposed mark is relatively clear, strong and low risk of potential for objections by your competitors or other similar mark holders. When you're firm on the brand name but beta testing the visual aspects - designs, etc., you can file an ITU on the name to place hold it while you finalize your branding. Depending on the state, you will also have some degree of common law (state) protection for your mark.