How do I make sure I don’t overdevelop one part of my body when exercising?

Just thinking about working in balance is the first step so bravo!

Because we don’t move in perfect balance all day, we all have imbalances in the body due to overdeveloped and conversely weakened counter parts of the body. The best way to work through this is to exercise with a series of counter-actions. If you move your body one way, make sure you move it the opposite way as well. For example, if you are doing bicep curls, you are working primarily the front of the arm by flexing at the elbow. To balance your arm muscle, you would extend at the elbow behind you to work the triceps and the back of the arm equally.

The best way to not overdevelop muscles is to spend as much time exercising the opposing muscle groups on each side of a joint. For every muscle, there in opposing muscle that does the opposite function. For example the quadriceps extends the thigh and the hamstrings flex the thigh. To prevent over development you should spend as much time working the quadriceps as you do the hamstrings. For every set and repetition you do for one muscle do the same amount for the opposite muscle. This will prevent muscle imbalances and overdevelopment of muscles.