I just got this game so I'm not that far into it.  What's the best strategy for the early levels?  Do I want to make a bunch of cupcakes first, or do I need to serve people and cash them out to get more people?

before the cafe opens, you have time to make a couple of batches of each cupcake.  When they are made take them over to the stand and click on the relevant picture.  To leave them there (in the display case)
 
Then when the customers come in click on each customer that want the cakes as quickly as possible.  I normally hold both trays of cakes and click on the customers in the line then replace the cakes, and serve the drinks.  Then click on the cash register.  The customers go and you quickly get a new line of customers.  As the levels go on you may want to make more batches of cakes before the cafe opens.  The display case holds 48 cupcakes of each type.  Also get your drinks ready (by clicking on the coffee etc...)  and get the sweets ready to give out if needed.
 
Don't forget to look out for boosts, on the top right hand side of the page.  The ones that I used where the cashx2, and the cake symbol.
 
Good luck. 
 
At the moment you can only post your medals for this game.  PF have still not given us a way of submitting our high score.  I have emailed them about this, but nothing has been updated yet.

What's the quickest way to make the cupcakes?  I'm trying to get expert on level 1.7, so I only have one type of cupcake to make.  How do you activate the 2X money powerup?

If you haven't chosen to design you own cupcake then this is the level, where you have pink cupcakes with a white icing and a loveheart topping. 
 
Click on the pink image on the cupcake machine, when they are ready click on the pink image again, and the cupcakes automatically are picked up, put them in the oven and click on the white icing and the loveheart topping, when the next batch of cupcakes are ready to go in the oven, click on the pink image again and then click on the oven, the baked cupcakes are now in your hands, put them on the table and click on the white icing again and the lovehearts, a new batch will be made while you have the others in your hand.  Click twice on the baked cupcakes and the icing and lovehearts will be put on one after the other, then when they are ready click on the display for the batch to be displayed.  Don't worry too much if the shop opens and customers come in.  Working quickly get 4 batches made and put on display.
 
The only drinks ordered in this level is milk.
 
When you have finished getting the batches ready, pick up two trays and click on every customers in the queue.  Then put them back on display and serve the drinks one after the other, then click on the cash register.
 
If any customer leaves a 2x money bonus, wait until you have served the whole next row then click on the bonus on the top right hand side of the screen and it will make a noise and start to shine to let you know that it is working then click on the cash register and you get double the profit.

OK, now I'm stuck on level 4.7.  There are three different types of cupcakes, I've been using my own and leaving off the toppers, but now I can't make expert doing that.