Many students may be able to solve simpler problems in the abstract form (i.e., using just numbers and symbols), so feel they don't need to draw a representation of these problems. However, problems increase in complexity as the curriculum progresses, and students may need to build on earlier models to solve new problems. It is very important that students are fluent in the early models, thus students should be drawing models for every real-world problem (unless noted by the teacher).

Models represent the problem, not necessarily the answer (though sometimes the answer can be seen once the problem is visualized). Make sure that your model contains all of the elements described in the problem. It often helps to model the problem one sentence at a time.

Practice is crucial! It will take a lot of drawing and practice with the different types of models to understand the power of modeling. Once you get it, it's an amazing problem solving tool and transfers quite nicely to understanding how algebra works.

Thinking Blocks from Math Playground offers a nice selection of problems to solve using bar models. This is a great way to learn how to use bar models without having to draw them.