[jldugger]

Time Management for System Adminstrators offers advice along the following lines (but it works for many technical support roles):

Find a like minded person and agree to a support shift: person A will handle interruptions in the morning so persona B can work on projects, then person B will handle interruptions in the second half of the shift so person A can work on their projects.

[reitanqild]

Written by Tom Limoncelli.

He and Christina Hogan has also written "The Practice of System and Network Administration" which deals with everything else schools didn't tell you about Systems Administration including chapters on hiring/firing, negotiations from both sides of the table and more ;-)