USE CONDOMS! That is the number one way to prevent herpes. Use a condom even for oral sex - it's lame, I know, but that's how I got herpes :/ It's unlikely that hand-genital contact would cause herpes, but putting a condom or glove on your hand will probably make you feel better in the long run.
Obviously, don't bang the girl if she has open sores or even a suspicious rash.
You may also want to take a shower right after sleeping with a girl. There is no scientific evidence to back this up as a prevention method, but it stands to reason that it could wash the virus off your skin if it hasn't penetrated to the nerve endings.
Keep your immune system strong. Sleep, good food, avoid stress, maybe also take vitamins or supplements. Sometimes your body can fight off herpes.
Even if you do all this, please understand, you can still get herpes. It's a very virulent little sucker of a virus. Even after using condoms, I would still recommend stopping by your doctor in a few months and getting tests for common STDs. Sex with prostitutes is a MAJOR risk factor for STD diagnosis in the United States, but because laws are different in Amsterdam, so the situation may also be different. Good luck.
Condoms are a must! But even so, this stuff still gets through and ruins lives. I'm trying to get a sense of what the risk might still be even wearing protection.
the risk from a one time protected encounter with someone who isn't having an obvious genital recurrence is incredibly small. I honestly don't know much about the testing done in their infamous part of town but don't hesitate to ask. It's probably also worthwhile to not skimp and get the equivalent of the $5 hooker too ;)
grace
Use of condoms cuts the risk by about 50%.
And I wouldn't say herpes entirely ruins lives :p You're talking to two people who live with it.