Always have the maximum number of appliances allowed, which is based on your level. The more appliances you have, the more you can cook at once.
Faster task completion
To complete tasks faster, enlist the help of friends. Enter to the social area and visit people repeatedly until you boost your social bar to at least two hearts. The higher your social bar, the more often your restaurant will appear on other player's social menus and more people will visit your kitchen.
Instant task completion
Advance the time on your device by the required hours or minutes to complete a task. Afterwards, set the time back to its correct value.