Everyone’s body is different.  Some people are small boned and will never have huge biceps no matter how hard they exercise.  You can, however improve how you look by doing the proper exercises. For larger biceps without injuring yourself, you have to exercise the bicep muscles from every angle. A lot of trainers in the gyms have you do bicep exercises that curl your arms, which only exercises part of your muscle.  You need to use good form.  Using the Preacher Bench to do your Preacher curls with weights, helps keep your elbows stationary which is very important.  If you do Concentration Curls, Seated Dumbbell Curls, Reverse Incline Curls, and Incline Dumbbell Curls and use a good bench, which you can adjust the angle on, for different exercises, you will achieve your goals over a period of time.  Be patient and use good form and you will achieve the look and the strength that you will have earned.