A Tire Puncture is probably the most common issue, and perhaps the easiest one to avoid. Punctures can be caused from hitting an obstacle with your wheel to riding over thorns, glass pieces etc. This can be prevented by using a good tire liner, and by making sure to inflate your tires to the recommended pressure, and annually replacing your tires and tubes. Also, replace your inner tube if you have had more than a couple of punctures. Another common related issue is recurring pinch flats which are flats caused mostly owing to riding on under-inflated tires. They are when the rim bottoms out and the tube gets pinched between the rim and the tire, and gets punctured.