2014 Update: Going Digital
Make sure everything important to you is stored in a published level!
I mention backing up your work later in this article, and recently personal experience has taught me that the only way to really make sure your creations are saved is by storing them in a published level. Because of a disk drive problem in my PS3, I recently switched to the digital version of Karting. I found that the digital version creates new Save Data on the HDD, and apparently the Data from the disk version is not compatible. Since there is no way to back up or import your "profile" like in LBP2, when you go digital you're starting over. Loosing costumes and Karts is a disappointment, but loading up and finding you moon empty could be heartbreaking. The good news is that everything published on your Earth will still be there, and you can copy those levels to your moon.
Fortunately I had almost everything useful I ever made in published levels, but the things I did loose are something of a set back - not to mention a real rage inducer.
The older info:
I'd like to give a few tips about LBPKarting Create, and highlight some very important differences from LittleBigPlanet in terms of saving your work.
If you created in the Beta, then all this will be familiar. If you're deciding whether to buy the game, you might want to read this first to avoid frustration later.
Instead of Rewind and Fast Forward, you have Undo and Redo
Undo feature only applies to the particular editor you're currently using. Once you've exited that editor, you will not be able to Undo. For example: You've created basic track and decide to use the Vertical Shift tool. While you're in the Track Editor you Undo and Redo - but once you return to your Popit menu, you lose the ability to undo those changes.
Normally in LBP, when I'm going to try out some major changes to my level, I'll press Start and Save As to a new location on my moon. This becomes even more important in Karting because of the Undo limitations.
See what did there? The limitations are undue
Save As feature does not exist in Create. The only way to save your level to another spot on your moon, is by returning to your Pod and using the Copy feature. Do this every time you've made progress that you don't want to risk losing before.
It takes a bit of time to keep going back to the Pod and making copies, but it also could save you the aggravation of making a non-undoable mistake right after you've achieved something brilliant.
Capture often when you're creating your own objects, don't rely entirely on level save files. I say this because I recently encountered a bug some creators may remember from beta, in which the objects in a level rearrange themselves. It sounds crazy, but it's true.
Pieces of material actually become scattered around the level, and decorations can also move in relationship to the material they were placed on.
It may help to Save from the pause menu before exiting the level, instead of simply returning to your pod and saving when prompted.
There is no Back Up Profile feature. What you can do instead, is to copy your Karting Save Data to a USB stick or other external storage. Then if needed, you can delete your Karting save data and replace it with the version backed up on your USB stick. I have tested, and found this works. You can also publish a level for storing your creations, then copy to you moon if needed. Note that you don't have to make the level copyable for other players in order to copy it yourself.
If you copy to another profile on the same PS3, everything on the moon will be deleted.
If you don't have an external storage device, I strongly recommend buying an inexpensive USB stick for backing up game save data.
The Trouble with Microchips
We know and love them from LBP2, but don't place too much trust in the Karting Microchip - like inlaws at your birthday party, Karting Microchips will overstay their welcome.
I recently built a lot of objects with Microchips holding Sounds and Effects Emitters. I found that sometimes when I place one of these objects and then later delete it, the Circuit Board from the chip will reappear after I've exited and re-loaded the level. The chip isn't there, just the circuit board - and everything on it works, so in my case I had random sounds and effects popping up in my level.
The Circuit Board cannot be deleted. It can be closed, but that doesn't get rid of it permanently. All the logic has to be deleted individually. This isn't so bad compared to other problems in Karting, but if you've got a lot of logic on a lot of unwanted Circuit Boards, it's time consuming.
To make things easier, I recommend that any large Microchips be placed on another chip. This way if you have the glitch, you can just delete the large chip off of the other chip's Circuit Board. It's much quicker than stripping away loads of logic.
And... When you've saved an object that includes a Microchip and then take that object from your popit, sometimes the wiring has disconnected itself. Most often this occurs when you have wires between two chips, but it can also happen within a single chip or between a chip and an object.
If an object you've saved has logic problems, check the wiring. I've created one object with some very simple logic and no matter how many times I redo the wiring and capture, the logic is disconnected next time I place the object.