Most personsal electric devices like cellphones and tablets are quite secure, to the point that if you lose one in a public place, you'll never get it back, not even if the most honest person on Earth finds it, simply because no matter how much personal data it may contain, nobody will be able to unlock it to find a way to contact its owner.
One solution is to tape an address label to your cellphone, like my parents have done in the past. But some cellphones just don't have a good surface for stickers, or the label can slowly rub off.
What I've started doing, and I would recommend everybody do this, is I edit the image I use for my lock screen so that it displays my e-mail address, and my wife's phone number. If your device has a removable memory card, put your contact information in a plain text file in the card's root directory. Name it @owner.txt so that it sorts before most other files and is self-descriptive. You can put a similar file in the root directory of other non-locking devices. This way, if an honest person finds your device and connects it to computer, your contact information has a chance of being discovered and used to get your device back to you.