Originally Posted by Stewie Mac

There is no 'transit' for dom-int'l connections at JNB - you will come out of domestic arrivals and have to walk landside to international departures, so you can easily go to the LH checkin area [if you already had your boarding pass, you could save a few hundred metres by going to a slightly nearer security/immigration area, but really there's not much in it].

Basically as you come into the arrivals area, baggage claim is signed downstairs, you can head upstairs (it will make sense when you get there), and then just keep walking through a shopping area, keep walking straight, you come to the central atrium which you walk around (you're above ground floor) and then head left towards international checkin.

It's very straightforward and you do *not* need a porter to help you!