I tip $5 for a short X ride and $10 for longer rides or XL, but my typical XL ride is a $40-$50 airport ride. And I'm also a driver myself, so I probably tip more than many riders. I also always tip in cash, so that the driver knows right away that I appreciate their service.
With Uber or Lyft, you can also tip in the app.
At the end of the ride, you will be prompted to rate the ride. Please remember that 5 stars is an "A," but 4 stars is an "F!" It really is -- if a driver averages 4.6 stars (92%, and an A in school), they are fired.
After you submit your rating, you will be given the option to tip in the app. With Uber, you can select from suggested tips, enter a custom amount, or set a prescribed % tip. If you tip in the app, the tip will show as a separate transaction on your credit card.
If you take Lyft, please tip your drivers in cash.
You can tip in the app with Lyft, but if the driver is trying to fulfill a Lyft promotion your in-app tip actually counts AGAINST the driver because Lyft counts it against the driver's income. The practical effect in that scenario is that Lyft gets 75% of your tip and the driver only gets 25%. A LOT of Lyft drivers don't read the promotion details and have no clue how the promotions work, so they are not aware that their tips are counted against them...but they are.
It's okay to tip in-app with Uber; Uber drivers get 100% of the tips.