Lay your traps in the least obvious place. But there's actually a deeper strategy here. The basic strategy is to lay your mines where they will be seen by tanks when it's too late for example, at the top of a ramp if you know that tanks tend to go up, more than they come down. However, if tanks like to come down ramps a lot, then place the mines at the top of the decline. The advanced strategy is to lay your mines off the side, so that visually, the coast is clear, but a nasty surprise is a bit further in.
Tanks think they're safe, so they drive forward only to die to well placed mines off to their side.
You also want to make sure that you place your mines in such a way that once they are spotted, there's little chance of a tank reacting. At the same time, you don't want to place your mines so that they're spotted too early, either. The key here is to lay mines so that once they are spotted, it's too late for the tank to react. Another tactic is to place mines around corners. Especially if you notice that tanks like to hug certain walls, in which case you can place the mines around the corner of the wall in question.