This information is based on CAD Layer Guidelines, Second Edition, Michael K. Schley, ed., published in 1997 by the American Institute of Architects in Washington, D.C.
All drawings which are created must be assigned a sheet number. The sheet number is also the drawing file name. Every project will likely have the same drawing names and thus the same file names. This can be confusing if you are working on more than one project (which is typical), so you have to be careful that you do not use a drawing from one project and save it over the same name in another project. You can easily separate drawings for different projects by saving them to a different folder for each job.
The first letter of a sheet number indicates the discipline name. Thus, a typical drawing sheet number would look like this: A101. This would be the first architectural drawing sheet, usually the site plan or the basement floor plan. Sheets should be numbered consecutively within a series from 01 to 99. The sheet number should appear in the lower left corner of the drawing.
Sheets in a bound set should be organized in the following sequence:
L = Landscape
A = Architectural
S = Structural
M = Mechanical
P = Plumbing
Q=Equipment (freezers, refrigerators, etc.: premanufactured items that are built-in and need to be connected to water, sewer, electrictity or gas)
F = Fire Protection (fire sprinklers, standpipes, fire extinguishers)
E = Electrical (power and lighting)
T = Telecommunications (telephone, cctv, cable, wired computer network, intercom, sound, and security)
I = Interior Furnishings
100 series: plans and reflected
ceiling plans (plotted at 1/4" = 1'-0" or 1/8" = 1'-0" scale)
200 series: elevations (plotted at 1/4" = 1'-0" or 1/8" = 1'-0" scale)
300 series: sections (plotted at 1/4" = 1'-0" or 1/8" = 1'-0" scale)
400 series: large scale "blown up" plans, elevations and sections (usually plotted at 1/4" = 1'-0", 1/2" = 1'-0" or 3/4" = 1'-0" scale)
500 series: details (plotted at 3/4" = 1'-0" , 1 1/2" = 1'-0", 3" = 1'-0" scale, half size or full size)
600 series: schedules and diagrams (no scale)
here for a list of standard layer names