Question: At the risk of potentially asking an off-topic question, I'd like to better understand the maintenance of a septic tank. I've never had one before and am unfamiliar with how to manage one. 

My primary question is: how often do septic tanks need to be pumped? We're looking to buy a 4/2 house with a concrete septic tank "supposedly" with a capacity of 2250. 

My secondary question is: how should septic tanks monitored? Just an annual scheduled service check-up? I don't want to spend money needlessly but also don't want to neglect something that needs regular attention.

Answer: 
The pumping question depends on your local codes. In our area, a brand new tank is good for 5 years before it needs to be pumped. A non-new tank must be pumped every 3 years. This is pretty typical.

I would say that tank monitoring will vary depending on your system. A septic tank is a pretty simple system. You have a primary tank (some call it a settling tank) that settles any solids out of the wastewater, and where most of your breakdown occurs (a well operating system will have natural occurring bacteria that do a good job of breaking down "solid" waste). As an aside, this settled goo is the majority of what is pumped out when the pump guy comes.

Usually, there is a second tank that is gravity fed, where the now "grey water" flows. From here, the grey water sits for a while (more breakdown occurs here) and it either feeds by gravity to a drain field, where it filters through the ground, or, it is pumped to a mound/elevated drain field.

In a simple non-pump system, you want to watch out for clogging in the outlets to the secondary tank and to the drain field. This can be done pretty easily- when you have the manhole covers replaced, ask the guy doing the work for you to tell you how for down from the top of the manhole, the drain is. Now, as often as you want, put a stick down the manhole, and see how deep the water is. If the water is above the drain, you have a blockage, and it should be serviced.

If you have a system with a pump, I'd highly recommend getting an alarm if one isn't installed already. The alarms will alert you if the level of the water goes above a specified height, which indicates a clogged pump or filter.

My recommendation would be to do your own monitoring (checking water level) as often as makes you comfortable, and have a scheduled service every 2-3 years.

More important than monitoring however, is making sure you are diligent with prevention. Use as little toilet paper as is practical, and stay away from quilted TP. Additionally, nothing but toilet waste, water, and TP should EVER go down your drains (the exception to this is if you have a food disposer, but even then, I'd use the disposal sparingly). Also, try not to use too harsh of chemicals when doing cleaning of your sinks/toilets/showers, and NEVER use draino.. there are cleaning products that are septic friendly, and septic friendly drain de-cloggers. Use them. This keeps the bacterial ecosystem breaking down your waste, nice and happy, which is a good thing.
MarkD already gave a really good by the book answer, but let me answer from the side of a homeowner who has had septic tanks for around the last 20 years.

The only time I had any maintenance/inspection was one time when my yard was getting really swampy. I had a septic guy come out and he pumped it rather cheaply, no permanent damage, no big whoop. Those Rid-X commercials with the bathroom full of backed up waste seem like an exaggeration to me.

We try to go easy on the chemicals, but we aren't that diligent about it. Definitely no drain cleaners, but chlorox goes in the toilets regularly.

One thing we do about 2-3 times a year is flush either some baker's yeast. It is effectively the same thing as Rid-X and much cheaper. I've also heard flushing raw hamburger (small quantities) is another way to get the bacteria going, but I'm a little nervous about that idea. I figure my septic tank gets enough hamburger the "regular" way if you know what I mean.