If you’re new to dim sum, it is somewhat like tapas where you’d order a variety of small plates to share; each dish is definitely not meant to be an individual meal on its own. Hence, portions are generally small and we recommend ordering 2 or 3 more dishes than the number of diners you have.
If you’re a larger group, it’s a good idea to order 2 portions of each dish so that everyone gets to try a bite of each one, as most plates will do about 4 pieces each. Another strategy is to order one of everything that seems appealing to figure out your favorites, and then dedicate the second round to the winners. Negotiating a strategy and your orders with the group, and compromising the odd leftover pieces are political exercises that are all part of the classic dim sum experience.