General recommendations. Before training, be sure to warm up your muscles. After that perform a warm-up set of the first exercise, using a very light weight, for 15-20 repetitions. Rest for a couple of minutes, and then you can start training.
Find such weight to perform the required number of repetitions without violating the technique. Make sure that the necessary muscles are working (they are marked in red on the animation). Perform the exercise smoothly. Watch your breath, exhale during the concentric (muscle-shortening) part. Try to keep your rest time between sets about 1-2 minutes. Do not work with heavy weight without help.
* For a detailed description of this exercise, click on the animation.