My best advice is to follow the typical business-to-business contacts sequence: call, mail, call.  That means it's best to initiate contact with business prospects by phone, then follow up with a letter or meeting.  Be certain to have good contact management software on hand so that you can create a database with prospect information.  You see, it will take as many as eight or more contacts with prospects before sales are closed, and you'll need to make frequent contact -- approximately once a month or more -- in order to move your prospects closer to ordering.  Once they have made purchases from you, you will still need to maintain contact ...and this is where e-mail comes in.  You only want to e-mail prospects who have given you permission to do so.  Plus, whatever you send must be relevant to their particular needs or they'll quickly boot it out as the spam.  Best wishes for success!