Hi GaryDB,
Relays create a back-EMF when they de-energise which can sometimes fry I/O. Power MOSFETS are much more robust for this application and will give you no trouble for this kind of application.
My recommendation would be the following:
1. Connect your I/O pin to the gate of an N-channel MOSFET. Include a pull-up resistor (i.e. to Vcc, normally 4.7Kohm is well suited).
2. Pick up a power relay that is capable of running at least 12V @ 1A (i.e. virtually any relay you will pick up off-the-shelf).
3. Connect one end of the relay coil to ground and the other end to the drain leg of the MOSFET. If your relay coil is polar, take care to observe polarity.
4. Connect the source leg of the MOSFET to Vcc.
5. Connect a diode and nominally sized resistor (e.g. 1Kohm) in series across the coils (shunted) with the diode oriented for current flow from ground to Vcc; this will preferentially dissipate any back-EMF through the resistor.
6. To energise your relay, simply pull your I/O pin low. This will energise the MOSFET channel and allow current to flow from the source to the drain (and then to ground via your relay coil).
In this configuration, you have a robust actuated switch with your maximum switching capacity governed only by the capacity of the relay.
Hope this helps!
Cheers,
Z