The Ticketmaster website offers an interactive seating chart for most venues where events are held. After you have selected the performance and the date, you can review the seating chart. It will be color-coded by section so that you can determine which section you are interested in. When you search for available tickets, you can qualify your search by a specific section.
If you want to select the actual seats within a section, the Ticketmaster website offers Official Platinum Seats for some performances. Viewable in a pull-down menu, the Official Platinum Seat are available in a separate list for you to select.
If you have poor vision or difficulty seeing from far distances, you may consider selecting a section that is closer to the stage. This way, your enjoyment of the performance will not be hindered by your vision issues. Also, if you have difficulty hearing, you may consider selecting a section that is closer to the stage.