Every warrior needs a master or a teacher. It is always easier to learn from someone else's example, especially the fundamentals. Comedians may have a harder time finding a mentor, but one way to benefit from professional comedians is by attending professional shows. Once you have established yourself as a new comedian, one should consider going to the club to catch a show on the weekend. It is smart to find out the club's policy on attending shows in advance; some clubs encourage their open mic comics to attend professional shows and do not charge a cover to attend (again, it is advisable to find out their stance on this prior to showing up to avoid appearing presumptuous). Another benefit to attending professional shows is being seen at the club. If the staff, manager or booker see you at the club, this may help you seem more legitimate as a comedian. Many try to pass themselves off as comedians after getting on stage a minimal amount of times, putting forth effort will help you appear more serious about comedy.
While at a professional show, watch how the pros work. Pay attention to the laughter. When it is at its peak, the comedian becomes silent, when the laughter starts to subside, then the comedian begins his next bit. Timing is a an important element to comedy. Timing can make or break any joke.