To tip or not to tip? Should I tip an airport shuttle bus driver? Really, since there are two entirely different animals when it comes to tipping airport shuttle bus drivers, we must break it down into which category you fall under.
Tipping the Hotel Airport Shuttle Bus Driver
These guys and gals are supposed to be personable, so expect that. They don't get any super kudos for doing so. If they help you load your stuff, they deserve a tip. If you only have a little bit, a dollar or two will suffice, if you have a lot, bump it up to five. If they provide you with a wonderful shuttle experience on the way to the hotel so much so that you are in a better mood, that deserves a little something too. Just regular small talk doesn't really justify anything. At a bare minimum, you should give them a dollar, unless you hated the experience and it was the driver's fault.
Tipping Parking Lot Airport Shuttle Bus Drivers
These fine people are in the bowels of the airport shuttle service. They ride the most uncomfortable buses and see the fewest sights. It's basically back and forth between point A and point B all day long. The hotel shuttle bus drivers at least get to see the town a little bit. People are also in a much worse mood between the parking lot and the terminal than they are between the terminal and the hotel. You are getting on a plane, you had to drive to the airport. Then you are getting shuttled to the terminal, where you will HAVE TO carry your stuff. Or, you are getting off the plane, you are tired, you have to get back to your car and drive home. This may be an hour or more. Realize that this is everyone's story. So that mood you are in is likely to be the next person's mood, too. As opposed to getting ferried to or from a hotel, where you will sit in a more comfortable van type bus. The point is, the parking lot shuttle bus driver sees people in a worse mood than the hotel shuttle bus driver.
So we have more sympathy for them. You should definitely tip the parking lot airport shuttle bus driver if (s)he lifts the slightest finger to help you. It is not his/her job to get out of the bus for any reason, so don't hold it against him/her if (s)he doesn't help you. But, definitely tip them if they do! And if they start up a conversation with you, that is tip worthy. Basically, have lower expectations of them, show them respect and courtesy, and if they reciprocate, they deserve something. It's going to mean more to them too. For the hotel airport shuttle bus driver, tips are customary. They are a rarer thing to the parking lot shuttle bus operator. They will understand and accept a tip as appreciation, not just money.