There are tons of biceps exercises out there but what is the most efficient. Well, it really depends on the situation.
The Hotel Biceps Workout
Here a few exercises for the biceps you can do in a hotel room.
Table rows - that exercises works your back and your biceps...and your grip.
Band curls - if you are planning it's a good idea to take some sort of an elastic band with you.
The below two exercises are also quite hard on your arms.
At the gym
My favorite biceps exercises are dumbbell curls on an incline bench - the hit the muscle pretty hard and you are more unlikely to cheat than when doing barbell curls. On top of that using dumbbells reduce a lot of stress on the wrist and elbow joint.