Great and small
It's hard for those of us who yum cha regularly to comprehend that dim sum was originally meant to be a snack: light dishes to accompany tea, rather than what it has evolved into: a meal that's accompanied by tea. Dim sum used to be purely Cantonese, but many restaurants serve dumplings, noodles and other xiao chi (small eats) from other Chinese cuisines. It also used to be eaten only from morning to early afternoon but the proliferation of all-day dim sum shops demonstrates an expanded demand.
While other snacks are fine to eat on one's own, it's a lonely experience to have dim sum by yourself. It's not only that the company is as important as the food, but also because dim sum orders come in two, three or four pieces per portion, and you can't taste many things if you are alone.
When ordering dim sum, take cooking methods into consideration, otherwise you'll end up with a whole meal of solely fried or steamed dishes. Ideally, the meal should be served from lightest to heaviest: so steamed dishes first, then baked, before the fried foods. Not many places will take the trouble to serve this way, though - the only time I've seen it was at Lung King Heen, at the Four Seasons, Central. Instead, you have to outwit the harried waiting staff and chefs, who want to cook and serve the food as quickly as possible. There's nothing to prevent you from ordering the dishes a few at a time - instead of all at once - which forces the kitchen to adapt to your pace.
In any case, dim sum should be eaten slowly, allowing plenty of time for sips of hot tea and good conversation.