Crewing is a key role and a valuable and important skill. You can either crew on an occasional basis or better still, become a much appreciated regular crew.
Crews work as a key member of the team, trimming sails and sharing in critical decisions, working the foredeck, tacking and backing the jib, managing the pole, holding the boom out on the run, gybing the pole and spinnaker and spotting obstacles and danger.
On the water a second pair of eyes is vital: What is the course? What are the other boats doing? How are they pointing? Where is the wind? Which way is the tide running? Where is the next racing mark? Where are the sandwiches?