But use your best judgment as to how physically intimate you want to get before telling.
One thing could lead to another, and you might find yourself in an awkward situation. The person you're seeing may beat a hasty retreat when he or she finds out you have genital herpes.
Keep dating, and you will find someone who wants to be with you regardless of your condition.
There are certainly some who wouldn't mind keeping the intimacy level just short of doing things that could transmit the virus.
Second, don't wait until you're just about to have sex -- in which case the attraction may be too strong for either of you to think rationally and act responsibly.