The robber: how to lose friends and make enemies in five seconds or less
Ah the robber, that pesky unit which you hate to see next to you city on that 6 brick, yet love to see stealing from your opponents. The robber is a means for players to keep one another from getting too far ahead of the back.
However, many times when you roll a 7 there won't be a runaway leader and you wll need to decide where to place it. Here is some advice with regard to placing the robber.
First, you should be placing a robber on a tile with a 5, 6, 8 or 9 since it will deprive your opponents of more resources that way.
Second, if an opopnent is currently competing directly with you for a spot to build a settlement, try to target them for the robber.
Third, try to place the robber on someone you know has a rarer resource, or a high amount of a certain resource you're in need at that time.
Fourth, try to hurt as many opponents as possible when placing a robber by placing it on a tile which 2 or 3 opponents have cities/settlements on.
And finally, target cities over settlements with the robber since it will stop more resources from being generated.