Remember:

Be sure to include:
  -reference designators (i.e. R1, R2, C1, U1, etc)
  -component values or part numbers
  -for ICs, each pin should be labeled with the pin name *and* number
  -straight lines (use a ruler)

Other advice:
  -If you scan/copy your schematic and turn in the copy, make sure its readable.
  -Don't just print the schematics provided on the course webpage and turn them in.
   This shows no effort.
  -You are drawing schematics, not a block diagram. You should not (for example) 
   replace the entire switch board with a block labeled "switch board."
  -If it is appropriate to combine multiple wires into a bus, you may do that. If 
   you combine multiple elements that are wired similarly (the eight diode+switch 
   pairs on the switch board) into a single element, make it very clear in the 
   schematic.

Bottom line, remember that these are to be "professional quality schematics."