If this is a mark that you're also using in Germany, you might look into using the Madrid protocol to nationalize it in the US. Germany is a party to the protocol. Alternatively, you can register it directly in the US through the US Patent & Trademark Office's "TEAS PLUS" system. You'd want to google those things.
As to what to do first -- (1) Make sure that nobody else is using the same mark on the same products, (2) make sure that the mark can be trademarked -- it cannot be merely a description or generic term for the product you sell.
For more information, the USPTO has a bunch of informational videos and other information here: http://www.uspto.gov/trademarks/basics/index.jsp