Details for writing daemons differ between Unices (including Linux) and WinNT/Win2000/WinXP.

Lincoln Stein covers the basics for Unix in Chapter 10, Forking Servers and the inetd Daemon, and Chapter 14, Bulletproofing Servers, in Network Programming with Perl.

There's a bit more to being a well-behaved daemon than is obvious at first glance. On page 312, Stein notes that a well-behaved daemon should:

1. "Autobackground" itself (fork/parent-exit), then close file handles and lose any assocition with a controlling terminal.
2. Change the current working directory to a known directory.
3. Change the file creation mask to a known state.
4. Set the PATH to a known state.
5. Record its process ID in a known place
6. Optionally use syslog to write diagnostics
7. Optionally handle HUP signals (e.g. to reload configuration files)
8. Options use chroot()

He then spends the better part of a chapter fleshing that out and giving examples.