To check your fluid level, you'll need to let your car cool down if it's been running, then access the engine underneath your hood [source: AutoMD]. How you open the hood varies with different cars and trucks, too (again, your owner's manual can help with this). There's usually a lever or button inside the cabin that's accessible to the driver, often along the left side. Once you find and activate it, you should hear the hood "pop" open.
As a safety measure, popping the hood is only the first step. Step around to the front of the vehicle and feel under the center of the hood. You'll find a lever that you need to move or pull until you can lift the hood up the rest of the way. Be sure to secure the hood so it doesn't fall back down. Newer vehicles sometimes have a built-in system, but others will require you to lift a brace to hold up the hood.
Next, locate the brake fluid reservoir. The owner's manual should tell you the specific location for your particular vehicle, but in most vehicles you can find it on the driver's side near the firewall (the wall between your engine and the cabin).
The reservoir itself is relatively small compared to other reservoirs and has a screw cap on top. It might not say "brake fluid," but you should see various instructions on the cap, the reservoir or both. These instructions tell you to clean off the cap before opening, while the other tells you what DOT type of brake fluid to use.
Cleaning off the cap before you open it helps keep the brake fluid clean and free of contaminants (including moisture), which can make your brakes work less efficiently and even corrode the interior of your brake system [source: Ramsey]. It could even lead to a failure of your anti-lock braking system [source: Weissler]. So be safe: Take a clean rag and wipe off any loose particles from the cap.
In the next section, we'll learn about the big debate among brake fluid connoisseurs and what category of brake fluid might be right for you.