You should know basic things about your car like, what size the engine is. Even if you are not an "enthusiast," Basic knowledge of your car will save you a lot of time, and money in the long run.
As a bonus, here's a few tips:
Avoid oil change shops. They use the cheapest filter available. Filter quality makes a difference, and you are gamling a $3K engine on saving $6 bucks for a cheap filter. If you have to have your oil changed by someone else, get it done by a Mechanic you trust, and have him put the better filter on it. Good filters include Wix, Purolator, and Mobil1. Avoid Fram. Get decent oil. Protip: Check to see if the house brand oil is made by Valvoline. You can save some money here, as it is often cheaper than "branded" Valvoline oil. Avoid SuperTech Oil, and for God's sake don't put Dollar General Oil in anything.
Check your oil when you get Gas. Oil is the Blood of the engine. It serves a lot of functions, and if it is leaking, find out where and why. While you are under the hood, look at the battery. Do the cable look like Cauliflower? Corroded cables won't carry Juice to the battery, or starter.
Speaking of the Battery, it is one of the most misdiagnosed problems on a car. Before you buy a new battery, get yours tested. Most auto part stores will test it for free. Many people want to replace it as soon as they have a problem, but if your alternator isn't charging the battery, you've just wasted a hundred dollars or more, replacing a perfectly good battery.
Gather what information you can about your vehicle before you go to the parts store. You may be surprised what the engine size matters on. For example, a Mitsubishi Eclipse has different brakes for the 6 cylinder than it does on the 4 cylinder, as part of a "Sports" package. Car manufacturers are completely incapable of "pick one and go with it." They like to have options. I have seen 7 part numbers for front brake pads on one vehicle.
Most car parts have 2 or 3 grades available. It depends on your needs as what's best for you. Are you getting rid of the car soon? Plan on keeping it until the wheels fall off? Just remember you get what you pay for. More expensive parts are often better in ways that may not be visually obvious, such as the quality or hardness of the metal.
It should go without saying, but make sure you fix the mechanical before spending money on the visual. It's always fun to see people dump $200 in stick on chrome skulls and purple dildo shift knobs, and yet they can't afford $70 to fix the O2 sensor that is causing them to get 6 MPG.
Check your tires. Are they bald? If they are underinflated, you are wasting money on gas. If they are unevenly worn, you have and alignment problem.
If you don't know much about cars, ask a friend who does to come with you when you buy a car. Buy them lunch for their time. They may be able to spot things that can cost you a lot of money, like antifreeze in the oil.
If you are new to your local area, talk to your local auto parts stores about what shops they recommend. They know who is a "Parts Changer" and who is a Mechanic. Sure, you may get some bias towards the shops that spend the most money, but the shops that spend the most money are busy. They are busy because they do a good job.
If you can afford to, always buy the better tools. This applies to any profession, not just auto repair.
Long post, but hopefully it can save you some money and time.