1. Doing too much, or not doing enough:
Like most things, when warming up, you can do too much, or nothing at all. It is important that your warm up does not detract from your actual exercise session and it prepares you for what is to come. You should aim for you warm up to have a rating of perceived exertion (RPE or how hard you think it is) to be somewhere between moderate to vigorous or a 6-7 out of 10.
2. Static stretching:
Static stretching has a time and a place: that time is not before exercise. Static stretching has been shown to reduce how much force you can produce (strength), your power and your strength endurance if performed before your main exercise session. All of these elements are often what we are trying to improve in an exercise session. Instead, when looking to acutely improve joint range of motion or flexibility prior to an exercise session we should adopt dynamic stretching. Dynamic stretches include things like leg swings and shoulder rolls.