Many people get excited starting out with weights and quickly pick up the most that they can. This can damage muscles and even cause other injuries. To find the weight that’s right for you, look for a weight that allows you to do 10-15 repetitions without strain. If you are shaking a lot or its painful at the end of 10 reps, try a lighter weight.
If you feel like you are in between 2 weights, you can use the heavier one with caution and do fewer reps.
Don’t forget to warm up and use proper form so as not to hurt your back or other muscles!