In nearly every single restaurant role, from waitress to general manager, everyone needs to be a master of time management. Being able to accurately measure how long it is going to take to do something and then executing in that time or less is cruitial. In a restaurant there is typically ten things you constantly had to have done five minutes ago. There is little time for someone to methodically complete one task at a time. You must be a fantastic multi-tasker and be able to get things done as soon as possible, in as little time as possible.
As a server you need to know when to send the order for the entrees, too soon and the guests will still be working on the salad, too late and they will be waiting on you. Cooks need to know when to start the steaks or the well done burger, time everything to come out of the kitchen at the same time. The host needs to know how long before the next table is free and an average wait time. The manager needs to know all of that and when to start the schedule so employees aren't waiting on them to know when they work.
When it's slow, you can't just sit around. You need to keep busy, manage your time, and always have the appearance of cleaning something. Anything looks better than standing around. If you can stay busy - you'll go a lot further than those that loaf.