So-
if your service doesn't need to be re-spawned, but you want it to start on boot:
create a script to start it and put it into /etc/init.d
strictly speaking it should accept one arguement, saying what to do: "start", "stop", "restart"
create symbolic links to the service and put them into /etc/rcN.d (for each of 2-5, or 3-5)
(debian simplification: update-rc.d servicename defaults)