I want to echo the excellent reply Rainflower made, but add a couple of other points. When and how to tell a prospective partner is different for different people. Some people prefer to tell upfront so that there are no misunderstandings, and if something develops then "The Talk" isn't a risk factor. Others prefer to get to know the person first so that their potential partner can know them as a full person first, and then fill them in on their medical condition later.
Whenever or however you decide to tell someone, it's really important that you do it (a) before you become sexual (including genital touching) and (b) when you're not in a sexually-charged situation. In other words, it's not a good idea to mention it ("Oh, by the way...") as you're locked in an embrace and ready to make a mad dash to the bedroom.
People tend to take their cue from how someone presents something about themselves. If you present it as something you're ashamed of and makes you undesirable, the person will pick up on that and respond to that. If you are clear in yourself that it's a medical condition that requires some extra attention and consideration, but doesn't change the wonderful person that you are, then they'll tend to respond to that too. It's not a guarantee of course, but it can help to keep from making an already difficult and awkward thing worse.
Check out the Resource Links (on the discussion listing page of the herpes forum here). Some of the links have a section about how to tell a partner.
Also, there is at least one online dating service for people with herpes out there. Many people prefer to only date people with herpes so that they don't have to have "The Talk." If you do a search, I'm sure you'll find it. There is one really good, reliable, reputable, established site out there, and a few fly-by-night sites that I'd be careful about.
Just remember: You're more than your medical condition.
TheOneInFour
| 
I'm Worried 
Linear Mode
