Keep the inks in it, keep it flat, if you can tape the head to prevent it from unlocking and moving (as it was originally) that's good, but if you're not sure about where to tape and what to do, then don't do it. Make sure the box can't move around during the drive.
Run a nozzle check and ensure the nozzles are all fine just before you pack it up - if not, clean until they're good).
Remove cables and all bits that can be so they don't rattle around, get broken etc. when packed up.
When it gets to your destination, let it sit for 24 hours for all the ink to settle, then do a nozzle check. If it needs cleaning, go ahead, if it looks like air in the lines, let it sit another day and then continue. The movement can stir things up.
Oh, and most importantly, have it specifically insured for the move. If you have an accident or big potholes on the road or whatever, your regular insurance may not cover it as being part of your vehicle contents.
