How do you get a good score on order score

Decorate your lobby nicely
Try to play a lot of mini games to get decorations or just buy them

Make sure that you are quick with the order, and get it to the costumer as soon as possible. Make sure your order is accurate and correct when you give it to your costumer. For improved scores you can also get upgrades on your machines, and thing to do in the lobby to improve your waiting score.
Hope this helped!

A couple of things:
Order station - This is your waiting score.
Be quick with taking and churning out orders. You do get deducted points for having a long queue waiting already, being slow to take customer's orders, and taking too long to deliver the finished order.

A good idea is to check out the exposition scene where your character flips the sign to open. They'll give you spoilers either about who your customers will be or what might be ordered, and you can arrange your schedule to make a start on those orders before the customer will actually arrive. If you don't remember the customers' orders, you can pause the game to check your customer list or the wiki. While they're walking in, you can select the cup, head back and let it automatically fill while you take the order. You can see clues to orders here - http://www.flipline.com/blog/archives/227

The other thing is to decorate your lobby with nice stuff that improves your waiting score.

Build station -
Try to be fast and aim for the green part. Don't wait for it to slow down - each second you wait deducts your score! Make sure you get the order right.

You can also decorate your lobby, but I personally prefer stuff that improves your waiting score.

Mix station -
Don't overmix!! You can judge whether it's a good idea to speed up or pause mixing by putting it back on the mixing queue rack (lefthand side). Make sure you double-check the blend and set an alarm if you aren't great with checking.

You can use some posters to decorate your lobby to increase your mixing score. I'd say it's a good idea to put some up as there will be times where your customers take ages to order things, messing up your schedule.

Top station -

Try to make things and spread out as possible. Try not to let things fall out. Put the right layers on in order (down to up on their memo). 

What I do is wait for the very first customer to walk in when I see who they are I immediately go to my customer book and look who it is and what they order the I go make that first put it in the mixer put the timer one then go take there order and wait for the next one. Now you won't be able to get everyone as soon as they walk in but don't worry you will get them. Then I do the same thing with the next one and once I take the first one off the mixer and get the other order I start doing the toppings and I watch with the bell how many customers have come in and I make sure there's no more than two. I usually get one out then have to do the other customer but after I get them there orders I go and do the one I didnt get the topings for, oh but make sure you don't send or take an order when a shake is almost done. I normally hit the button that make it go faster then take it off and take or send an order.