Each month, pilots have an opportunity to "bid" their schedule approximately a month in advance. Crew Scheduling publishes a list of what are called "lines of time". "Lines of time" are a monthly schedule comprised of "rotations" and days off. They are produced for a specific aircraft for each pilot base (or "domicile").  The L1011, 757/767/777, and MD-11 crews typically fly long-range trips(and international) while the 727, 737, MD-88/90 crews mostly fly the shorter trips.  We can choose pilot domiciles at Atlanta, Los Angeles, Cincinnati, Dallas, New York (covering EWR/JFK/LGA), Orlando, Salt Lake City and Portland.

For example, I would be issued a Pilot Bid Package from which to list in rank order which schedule I would like to fly. During August 2000, there are about 193 lines in which to choose of which 136 are "regular lines of time" as listed below and 57 are "reserve" lines where  you are on-call to crew scheduling during certain days.

You can enter your schedule choices via your home computer, over the telephone or through the computer terminals throughout the pilot lounge and headquarters.

Here is an example of a line of time from August 2000:

This line of time is 15 days off and 4 rotations long.

I picked this line of time for simplicity. It only involves four occurences of one rotation. The rotation is as follows (copied from an actual bid package):

I generally trip to bid lines of time that contain trips which make it easier for me to fly from my home in Phoenix, AZ the day of the trip and then return home the evening the trip finishes. I also prefer MD-90 trips because the -90 is much nicer to fly than the -88. Also, a definite plus for a trip would be avoiding ATL (yes, this is possible before anyone writes to ask how does one avoid ATL and still work for my airline!) and doing more west coast flying like SAN (San Diego, CA), ONT (Ontario, CA), or SNA (Santa Ana/Orange County/John Wayne, CA).

This is an example of a reserve line of time:
 

On your reserve days, during the first day of a series of reserve (for example, on November 6th), you are on what is called "Short Call".  "Short Call" means that you have to be "readily available".  Crew Scheduling can call you and expect you to be able to fly a trip within 2 hours after notifying you.

On the other reserve days, you are on "Long Call".  This means that they have certain "windows" during which crew scheduling can notify you and assign a trip.  So on the long call days during the "window of availability", you have to be able to be reached via a pager, cellular or home telephone number.  During November, the reserve "long call" windows are between 9:00am to 12:00pm and from 6:00pm to 7:00pm.
 
If you ever would like to fly a different aircraft or change your base, you can put in a request in the computer called an "Advance Entitlement" which indicates that if you have the seniority to fly a specific aircraft in a specific pilot base, you would like to enter training in the next available class.