1. Never lift the weight. It sounds crazy but it works better if you think of it as contracting your hamstrings and if you contract it hard enough the weight will move. Use weight as resistance so you can contract harder.
2. Proper form is everything. Your knee joint should never move forward of your hip joint. If you are laying down doing ham curls then force your pelvis into the bench, do not lift your butt off the bench surface. If you are doing standing curls, do not stick your butt out, again force your hips into the machine. If you are doing seated curls don't arch your back excessively.
3. Always keep tension on the muscle at the top of the movement. It's easy to let momentum move the weight but the last half of most hamstring exercises give your hamstrings the development it rarely gets and you definitely want.
4. Never pick a weight that is too heavy to do the reps in complete control. You should be able to stop the exercise any time during the movement and be in complete control of the resistance.
5. Warming up and stretching is vital to complete hamstring development as well as avoiding injury. Take time and do it right.
6. Instead of doing quad work first, hamstring training is always first before anything else. Quads come after hamstrings so you never run out of juice during a high intensity hamstring workout. Hamstring training is not anywhere near as taxing as quad training.
7. Quality of the movement is always far more important than the quantity of weight used. Hamstrings grow like weeds if you train them properly, in control with full range of motion and peak contraction.