My husband and I have several Kindles and Kindle apps between us. I have a Kindle Paperwhite that's my primary reading device. I also have a Kindle Keyboard that I keep mostly for proofing using the read-aloud (text-to-speech) feature. My husband has a Kindle Touch (it used to be my Kindle Touch), and a Kindle app on his iPad (great for cookbooks and other books with color illustrations). I also have the Kindle app on my Android phone, although I don't use it much because I generally carry my Kindle in my purse.
That's five devices! When you buy a book from the Kindle store, there's a default device listed under the "Deliver to" link. If I don't want the default device, I need to click the arrow and select which device to send the book to. I can't tell you how many times I sent a book to the wrong Kindle! Admittedly, it's hardly a major problem, but still, it can be annoying, especially if you don't realize you've done it, and then the book isn't there when you fire up your Kindle. My husband's Kindle kept showing up as the default, and I bought a lot more books than he did, so it was frustrating to keep doing that.
I once emailed Amazon to ask how I could reset the default device, and the customer service person told me there wasn't a way to make my Kindle the default. I don't know if that person just didn't know or didn't understand my question, but actually there is a very simple way to set which Kindle shows up at the top of the list because is displayed alphabetically! All you have to do is to change the Kindle's name. Someone pointed this out in a user forum; I wish I could remember their name to say thanks.
To reset your Kindle's name (or Kindle app's name), just go to the Manage Your Devices link on your Amazon account page (left column).
Once you click the link, you go to a page where all your Kindles and apps are listed. The first column is the Kindle name, which is something you can edit as often as needed, just by clicking the Edit link right after the name. To make a Kindle or Kindle app appear first, just be sure it's first alphabetically. I simple added an “a” in front of my name, but you could also rename your Kindle “Amabel” or “Aaron,” or whatever you like.