Be sure to identify all of your key competitors for each of your products or services. For each key competitor, determine what their market share is. Then, try to estimate how long it will take before new competitors will enter into the marketplace. Finally, identify any indirect or secondary competitors which may have an impact on your business's success. The strengths of your competitors are also competitive advantages which you, too, can provide.
Weaknesses are simply the flip side of strengths.
In other words, analyze the same areas as you did before to determine what your competitors' weaknesses are. All of these can be red flags for any business. If you find weak areas in your competition, be sure to find out why they are having problems. This way, you can avoid the same mistakes they have made. If your target market is not important to your competition, then you will most likely have an open field to run in if your idea is a good one.