These strength workouts are designed for you to be able to do them anywhere. You do not need any weight equipment in order to do them and they will be highly beneficial if you do them regularly. The key to building strength is consistency.
Consistent effort is what generates consistent results.
Always record your workouts with the exact number of repetitions and rest that you did. It is much easier to chart progress if you have a record of what you did. Use your stomach muscles to raise yourself up not momentum. For the oblique sit-ups, place your feet on a chair with your knees rotated left for the left side and right for the right side. It is better to do 15 sit-ups correctly than it is to do 100 incorrectly.