Are you concerned about partnering because you don't want to expose your customers to a potential competitor or you're not sure you know the other partner well enough to take the risk?
These are common concerns when considering a partnership with another company. The easiest way to alleviate these concerns is to set up a face to face meeting in order to get to know each other better, and to take time to outline rules of engagement, roles, responsibilities and compensation structure for the partnering activities. Of course not all deals will be the same, and you will need to consider building some flexibility into your plans. There is no better way to begin the process then to bring everyone together to gain some familiarity with each other and your business models. That way you can hopefully learn enough to determine if you wish to partner and how you want to go about doing it.