Two Ways: The First might not work if you have the LPT grng to the chassis or if the 5+ can find ground else where, If the spindle is on even when the relay is off then this is prob the case.
Quick Ascii drawing, but basicly you tie 5+ to the lpt pin, thought the relay to the resistor and finally to ground. This should limit the current the lpt pin pulls.
5v+
|
\/
(LPT Pin) ---> (Relay Positive Lug) (Relay Negitive lug) ---> Resistor ---> Ground
Two:
Vcc (Of what the relay's coil is rated for)
|
+------+
| __|__
Relay /^\ Diode 1N4002
Coil /---\
| |
+------+
|
Diode | /
1N4148 4.7K B |/ C
parallel >-|>|-+--\/\/\/- -| NPN Transistor: BC547A or 2N2222A
port data | |\ E
pin +-|<|-+ | V
1N4148 | |
parallel >-------------+---------+
port ground |
Ground
And more examples @
http://www.smendes.com/el31p/parallel.htm