It depends on mileage but 10-12k miles per year is assumed to be average; if you're doing that then 12 monthly oil change should be ok. If it's a lot less, change the oil more often i.e. 6 months, to flush out the settled crud in there.

I used to do my Focus oil change every 12 months and it was fine. Some say the Focus drinks oil, but I never had any problems with it.

I was under the impression that the spark plugs ought to be checked and changed if necessary every 12 months too....33k miles might be a sensible maximum for changing them (that's about 3 years for your average driver).