I am 26 and I drive my Tesla Model S on the Uberx platform in Seattle (No uberPlus or select here). I used to never get tipped, until I learned the secret. Pay me $20 and I will tell you...

Just kidding! The secret is to make sure your passengers know that other people tip you. That is the strongest motivator for a tip. I do this in three ways:

1) I have cash in a cupholder. Not 1's. A couple 5's. Nobody has ever tried robbing me. This does two things. It shows that other people have tipped, that it was spontaneous (it's not in a jar or something) and that if someone wants to hand me a $20 bill I have change.

2) I have a cheap tablet in the back for people to browse the internet, play music through my Google play account etc. with a card reader on it. If people ask about it, I explain that they can tip me through the Square app.

3) When I get the annoying "so do you like being an Uber driver" I say that it's like any other service job, you have good nights and bad nights. Lately people have been tipping me a lot, which is surprising and awesome.

Doing these exact things may not work for you. You need to play off your strengths and weaknesses like I play off mine. If you have small kids, put a picture of them up and talk about how you do this to save for their future education. Whatever. Just make it work.

You deserve to be tipped. Taxi cabs charge 2.5x the fare, offer shitty service, and still get tipped the "obligatory" 20% because people just expect it.