While I'm not sure if my travel patterns are typical or not, when I am traveling domestically, I usually only spend one or two days in each city.  Typically, I am travelling for a single meeting, make my plans and fill in other meetings opportunistically around my schedule.  That has a couple of implications.

First, I spend a lot of time on planes.  Like everyone that spends a lot of time on planes, if I am not productive on the plane, I will fall behind on my work load.  The number one key for being productive (for me), is to be in the right seat.  The key to getting the right seat on most airlines is Airport Checkin Time.  For most airlines, the early bird gets the worm.  For upgrades, airport checkin time is the usually the tie breaker for all passengers at the same frequent flyer status when going down the upgrade list.  Additionally, there is always a decent set of really good seats that are held back under airport control, waiting for passengers with disabilities, special needs, or unusual circumstances.  Many airlines use checkin time to dole those out.  Others, allow anyone (sometimes restricted by status) to have access, but only after they have checked in at the airport.

Second, I am always pressed for time.  Because I tend to wedge meetings, conference calls, and other activities into every nook and cranny in my schedule, I am always running late to the airport.  If there are no kiosks, or there is a long line to self checkin, or if I get the dreaded "please see a gate agent" error, I can easily end up spending an extra night somewhere I wasn't planning.

One travel hack I use all the time to combat these two problems is checking in the day before.  Most airlines (though not all) allow checkin 24 hours in advance.  This is primarily geared towards checking in online.  While checking in online and printing my boarding pass helps with the second problem (time pressure), it generally does nothing for the first problem (seats).  (Of course the big exception here is Southwest Airlines.)  While some airport kiosks won't allow you to check in until day of departure, I have found that in those cases, the agents in the airline lounge can often be pursuaded to print your boarding pass for you.  If you are at the highest tier of your airline frequent flyer program, this essentially guarentees you an upgrade if one is possible.  There is nothing like showing up for a 6AM flight with an airport checkin time of noon the day before.