Whilst this is a purely aesthetic concern, it is part of Beachcamp's objectives to get in good shape for the beach including your upper body. For the guys this likely means developing an impressive pair of guns, whilst for the girls this probably means banishing the bingo wings without building too much bulk.
Building muscle and toning muscle require different exercise techniques, and so doing the right exercises can make all the difference as to the shape you achieve.
To build muscle: The most effective training, in my opinion, is pyramid training with free weights which involves decreasing reps with increased intensity. This is the training used in the Body for Life programme and is most effective when combined with frequent protein intake. All the details can be found on their site: http://bodyforlife.com/library/exercise/weight-training
To tone muscle: If you don't want bulging biceps but do want toned arms then you need to do lots of reps with low weights. This is the premise behind the Tracy Anderson Method and also the weight training in The Bodydoctor
programme, which is a great all round toning programme with good instructions on proper weight training technique.
Whichever you go for you need to train your upperbody at least twice a week for decent results so some commitment is required, although just doing 30 pushups each evening at home will yield surprising results.