I changed the job title in the subject because the press (and therefore, the public) largely refers to 'us' as "line judges" in lieu of "line umpires" (the USTA's name for this type of official).
To get hired to work at a USTA or ITF event, a certified line official has to apply via the USTA Officiating website, which lists the tournaments' locations and dates as well as their supervisors, referees and chiefs, in most cases. These are the lower level up to ATP Challenger tournaments.
As previously mentioned, the chief does the hiring and it's largely a "people business" which requires networking to get your first and then subsequent assignments until you've received a number of grades, e.g. a track record of competent performances. If you've worked enough to establish yourself as a capable official, you should get added to the list of line umpires eligible to work on the ATP and WTA tours, at which point you'll get access to the way one applies for those events.
You'll be notified via email that you've been selected for an event; this usually occurs at least 4 weeks prior to the event. If you're a busy person, you may have to block your calendar in anticipation of being selected so that you won't have to decline the assignment (declining assignments may have a negative effect on your chances of being hired for subsequent events). Your assignment will be anywhere from 1 day to the total number of days for the event.
After accepting your assignment, you should expect to receive an email from the chief at least one - though it's usually two or more - week(s) in advance of the event with information detailing the hotel and tournament site information, and (at least the) first day report time. Almost all hotel rooms are assigned for double occupancy, meaning you'll be rooming with another official of the same gender during the tournament. Sometimes there is an option for you to pay the other half of the room rate so that you can room by yourself or bring your spouse etc.. Typically, you are booked to arrive the night before the event through the night of your last worked day ... since the last day might be long and/or rain delayed, and you'll be able to return to your room to shower and sleep, e.g. before returning home the next day.
You'll be expected to report to the tournament location by the time specified, usually an hour before the matches are scheduled to start on the first day (30-45 minutes before the matches on subsequent days). There will be an orientation meeting led by the chief with an appearance by the referee and/or input from the chair umpires as well. These are frequently learning opportunities, though much of what is conveyed is the same from tournament to tournament.
Each line umpire will receive a crew sheet that details who is on each team as well as the courts and times to work throughout the day. Each crew has a chief - chosen from among the line umpires - that is responsible for assigning that day's line umpire positions on the court for each time slot; these time slots are referred to as rotations. The number of umpires per crew depends upon the level and stage of the tournament: higher level tournaments have more line umpires on court and so do the later stages of the event. The crew chief is also responsible for filling out each rotation's 'blank' evaluation sheets, which are to be handed to that court's chair umpire at the start of the rotation.
In my next post, I will describe how the evaluation system works, and some of its nuances ...