For the following I assume a conference with at most a few hundred participants that is well organised, i.e., early poster session(s), and posters can stay on display for the entire conference.
In my experience, there are basically two kinds of “customers” you can attract with a poster, with little middle ground in between:
People for whom skimming your poster suffices that they want to talk to you about it. These people will usually make an effort to contact you even if you are not present at your poster or if you are busy at the moment they are visiting.
People who get lured into a guided tour of your poster by you talking them into it or by joining a running guided tour. Importantly there are some people who are much more likely to join a guided tour than to ask for one if you are alone at your poster.
The last point leads to a positive feedback loop (customers beget customers), which in extreme cases can lead to such situations as I once experienced: I hardly got any customers during the first half of the poster round (partially due to my poster being in a unfavourable location) and afterwards I was overrun and busy until long after the official end of the session.
With this in mind, I suggest:
In the beginning, stay at your poster and shamelessly try to talk people into guided tours. When everything else fails, explain your poster to the author of the poster next to you (and vice versa). If everything goes well, you will be busy for the entire session.
Only leave your poster if it becomes clear that the majority of the audience has stopped browsing posters, so you do not get any customers of the second kind anymore. Be patient; if you are amongst the first poster presenters to do so, you are almost certainly doing it to early.
Make it very easy for customers of the first kind to contact you: Put your e-mail address and a portrait of you on the poster.
Find out early which other posters you want to see. Most conferences facilitate this by either publishing abstracts of posters, having a poster flash, or allowing posters to be displayed before the session. This way you can solicit guided tours of those posters from their owners outside of the poster session. Ideally briefly inform the owners of your interest before or during the poster session – this way both sides can work towards it.