It depends on the type of fluid and level of contamination or heat. if there is no problem with the fluid it should be left alone!
Most car makers recommend that the brake fluid be changed every two years. The make/model of the vehicle is not an issue, it is just that brake fluid has a "life span" of about 2 years once it is in use. Brake fluid is "hygroscopic", which means it absorbs water from the air, so after about two years of use it needs changing.
PS should be 18000 miles and brake fluid about 30000 miles PS should be 18000 miles and brake fluid about 30000 miles
When its old
The best advice is to follow the manufacturer's service interval recommendations. Fluid should also be changed if it appears dirty (new fluid is nice clear yellow) or the cap has been loose on the reservoir (as brake fluid is hygroscopic and will absorb moisture from the air, rendering it ineffective). Find a mechanic you trust and follow their recommendations.
You do not need to change it at all, unless you have replaced some long brake lines. Just make sure that the level of the fluid is proper.
You add it to the master cylinder mounted on the firewall, drivers side. Do not overfill, and only add fluid from a sealed container. Use the proper fluid as listed on the master cylinder cap. If it is low of fluid it means that you either have a leak or the brake pads have worn down, and they should be checked. You may need to have your pads replaced. Fluid does not evaporate and those are the only reasons it will be low. This car is 16 years old, and if you have not had the fluid changed it is way over due. Have the entire brake system flushed and fresh fluid installed. Brake fluid should be changed at least every 3/36. This is an often overlooked service.
Automatic transmission fluid should be changed according to the manufacturer's suggestions. Many manufacturers suggest having the fluid changed at every 100,000 miles.
You should check your brake fluid every three months to make sure the levels are okay. If the levels are down, replace the fluids immediately...better safe than sorry.
Every 5000 miles.
once a year
Check the Color if it is Dark or Smells Burnt then it should be changed. Related [http://wiki.answers.com/Q/When_must_power_steering_fluid_be_changed_if_ever Question and Answer]
Usually it's low brake fluid or a problem with the abs. Check the brake fluid reservoir. Often the brake fluid will go down as the brake pads wear and the calipers has to travel further.