You do not need to be at the gym to get yourself buff. Here are some exercises that you can do to tighten, tone, and build up your biceps without having to fight for dumbbells in the gym.
Just be sure to use weights that you can easily carry without having to exert too much effort, but heavy enough to challenge your muscles.
Dumbbell Curls: Stand up straight while holding the dumbbells at your sides, and your feet placed slightly apart for balance. Hold the dumbbells at your side with your palms rotated towards to your side. Keep this as your starting position.
Exhale as you slowly curl your right arm to lift the dumbbell up to shoulder level, rotating your wrist as you do so until it is facing upwards. Hold the peak position for a second, and inhale as you slowly go back to starting position while counteracting the force of gravity. Alternate the sets between arms by completing one set in your right arm before proceeding to do a new set at the other.
Concentration Curls: Sit on a chair or a bench with your feet placed apart wider than your shoulders. Hold a dumbbell in one hand and lean forward with your upper arm resting on your thigh. Position your arm so that your elbow is below your leg with your triceps leaning against your inner thigh.
Extend your arms down towards the floor while maintaining a slight bend at the elbows. Keep this as your starting position. Exhale as you curl your biceps in a slow, controlled motion until your hand is at the level of your shoulder, being careful to keep your upper arm stationary. Inhale as you go back to starting position.
Preacher curls using an exercise ball: Preacher curls are great for training your biceps, and they can be done even without a preacher bench. All you need is a good exercise ball and you are all set. Sit on a low bench and place the exercise ball in front of you. The exercise ball should be at chest level, the same height as the arm rest of a preacher bench.
Hold the dumbbell and place your arm on the exercise ball with your elbow at the center and partially extend your arm, maintaining a slight curve at the elbow. Rotate your wrist so that your palms are facing upwards. This will be your starting position. Exhale as you slowly curl your arm until the dumbbell reaches chin level. Hold the contraction for a second and inhale as you go back to starting position. Finish a set, and then repeat in the other arm.
In all of the exercises, take care not to use momentum to force the execution of each movement. It is best that you do slow, controlled motions to further isolate the motion in your target muscles without using other muscle groups. The exercise is done with 2 sets of 15-25 reps.