Well there are normally two modes of action I will take:
I have never gotten a call from anyone saying I gave them an STD, and in general I try to avoid this.It really depends on the arena though:
The shady-risk arena:
Lets be honest, this is the arena that revolves around hookup sites, and saunas, and video arcades, etc. I'm not partial to all of these places for sex, but I will dabble on the hookup sites when I'm in that mode. Been to saunas outside of the states. You know the rules of this arena. Its basically buyer beware, and you can get an std via a blow job, or frottage. I try to be as safe as possible, but once in a while, i'll do something a little risky (like finger someone), or let someone go down on me really deep. The most frequent I've hooked up is 5 times a week for X amount of weeks (i'm not saying). The average though was 2 times a week. And if i had any type of symptoms, I'd stop.
The high ground arena:
These days: I normally wait around 2 weeks, just to knock out the high risk STDS (the ones that normally would show by then). This arena involves some sort of date situation or a more "social hookup". I find it makes the sex better, even if it is temporary. For the stds that take up to a month to show, I'd just have to apologize about if i passed it on to someone. I still try to be as safe as possible, but I'm partial to some things, fingers, etc.
It took a couple of rounds of the shady arena to get me to this point. I normally don't mix the two different modes. I'm either playing or "dating". Of course when I'm in a relationship its a whole different cup of tea.
That's how i do it.