When you get off the interstate/highway there is usually more than one station to choose from. I look for the one that has the easiest on/off access back to the highway assuming they all are reasonably competitive on price. As you approach the pumps, when in doubt look for a rig bigger than yours, I like the outside lane. If you pull in to pump will someone accessing the parking in front of the station store block your ability to swing wide enough to get back out?
As noted above never get below one quarter of a tank as this will leave you with more options. Usually one of us will need to stop before we get that low on fuel. :C