Getting students to be better problem solvers can be a big task. It is important for us to give kids chances to solve non-routine problems. One way I like to encourage problem solving is through games. If I have stations set up for class, I usually have a teacher-led station, an independent station, and a "game" station (or as the kids call it, the fun one!). Using games that require practice of specific skills or use strategy are best for helping build mathematical skills.
If you don't have time to teach each group how to play a game, try using the "Fishbowl" strategy. I pick one group of students and have the rest of the class gather around and watch as I show the selected group how to play. Then the selected group plays a round or two while the class watches as if they are looking in on fish in a fishbowl. This way everyone knows the rules and how the game is played.
Here are some games I have used that involve using a strategy:
Snap it Up
Traffic Jam/Rush Hour
3-D Tic Tac Toe (my students love this one!)