In a sense, going to your mechanic is a bit 'like going to your doctor. Just as you describe your symptoms to your doctor, you must also describe the symptoms of your car to your mechanic. How do you think the questions that your doctor does not ask, in order to identify the problem, a mechanic needs to get the same information about the problems with your car. For example, when reporting a symptom with your doctor, you describe where the problem is, what kind of pain it is, how much time has gone on, and other information that may be useful.
Similarly, note the behavior of your car. Remember both changes in the behavior of the car, as well as any associated noise that happens simultaneously. For example, the simple problem of a puncture has a distinct fluttering noise, and is accompanied by a problem of very precise steering. Not all problems are both components. One of the first signs of a problem common CV is a single click noise while the machine makes a strong right-handed or left-hander. However, many problems of cars have both a behavioral component and sound to them, so as to listen carefully and feel any differences in the operation of the car. (If a CV joint problem is left unattended, there can be a significant performance difference if you grab the wheel and not more shifts, but we hope that the car is allowed to enter in that condition!)
In addition to this, try to accurately describe where and when changes happen to your car. For example, the CV joint above problem occurs only when the car is taking a bend. Furthermore, the position of the grasped clicking noise which indicates constant velocity joint is a problem, if it is on the right side or the left side. It 'important for the mechanic to know that some problems only occur after the car has been driving for 10 minutes, or occur as the machine starts and then it goes away, or other time-dependent behavior.
Try to be as descriptive as possible when talking about the problem, although it seems a bit 'stupid. The old joke about a woman talking to your mechanic, and describe a sound like a bowling ball that rolls into the trunk, only to discover that it was actually a bowling ball rolling around the trunk. However detailed description is of great benefit. If the noise sounds like marbles in a cardboard box, or a bunch of safety pins that fall on the floor, so to speak. One of these phrases can cause a time "aha" for the mechanic diagnose the problem and make it really easy.
A list of common descriptive sounds that can be applied to a machine are: clicking, screaming, growling, hissing, throbbing, humming, chirping, noise, or knock. The smells that may be reported to your mechanic are: plastic fuel oil burning, a putrid smell, smell or other strong or mild. Finally, if something looks unusually hot to the touch that should be communicated to the mechanic. (Do not touch the metal parts in a running or just drive off with your hand can be easily hot enough to burn you.)
If your car is not running at all, try your best to describe what the car sounded, felt, and acted as before the machine has failed. These descriptions should help your mechanic as quickly and correctly solve any problem your car currently has.