Bakery Door Trick:
The following trick will help you if you don't have much time or you are not making food, or your ovens are full. To perform the glitch you have to put something in front of your Bakery's door like a cash register for example. When the door is blocked nobody can get in so they wont give your bakery a bad star rating. Doing this allows you to level up faster because you won't get bad ratings. When you have sorted out your bakery and are ready for more people put the item blocking the door back to it's place and re-open.
To earn more Gems:
Every time when you enter to play bakery story or restaurant story, there be a pop up message and it tell you to download a game (example Ninja's Live) and get 6 gems free. Install that game, open it and go into the game until you reach another pop up saying earning 6 gems for Bakery story and Restaurant Story... Click 'ok'. Once that is done, uninstall the game (Ninja's Live) and you will received 6 gems.
The Door Trick:
Let's say you don't have any food on display, and you're still cooking some... You don't want a bad rating, right? Well, you don't have to have one. Go to the decorate screen and then put something in front of the door (like a counter). Customers can't get in, and you keep your rating.
Make food faster:
If you make for example Chocolate Cake, which takes 1 hour, just click home>general>date & time and set it one hour ahead!