As an alternative to the standing dumbbell curls, you can perform them seated on a bench. The execution is much the same as the standing dumbbell curl exercise.
Seated Dumbbell Technique & Execution
Sit on a bench with a dumbbell in each hand extended at arm's length
Start with your palms facing toward your body and keep your elbows steady
Curl the weight up and twisting your wrists during the movement so that at the top of the lift, your palms are facing you
Lower the weight back to starting position
You can do this either alternating each arm or curl both arms at the same time
Incline Dumbbell Curl Exercise
Similar to the seated dumbbell curl, this exercise is performed on a incline bench - you can also set different degrees of incline for this exercise. Performing seated dumbbell curls as these forces you to execute the exercise movements with strict form. This prevents you from swinging your body to generate momentum to lift the weights as you can in a standing upright position. Because of this, you may need to use a slightly lighter weight compared to what you use for standing dumbbell curl exercises.
You can perform this exercise curling both arms at the same time (above), or you can perform alternate dumbbell curls (below).
Incline Dumbbell Curl Technique & Execution
Sit on an incline bench holding a dumbbell in each hand
Curl the weights up to shoulder level - you can do this either with both arms at the same time, or perform alternate dumbbell curls
Lower the weight back down to starting position
Throughout the exercise, avoid swinging your arms to gain momentum to help with the curl - you can prevent this by pausing very briefly at the bottom of each rep