Downshifting is a skill that will benefit you if used correctly. First thing you need to know is how to drive a manual transmission. Downshifting can actually be good for your transmission and can make your clutch last longer. Every car has a powerband which is usually between 4,000 and 6,000 rpm. Thats pretty much the range you want to try to keep when driving standard. If your rpms are pretty low than you aren't going to go that fast. You might actually stall out your car. Thats when you should downshift to get your rpms higher and where they need to be.
Step 1: Clutch, Brake, Gas
In a standard car there are 3 pedals unlike automatic that has only two. The far left is your clutch. The clutch is used when ever you have to shift to any gear including neutral. Your clutch is important when downshifting since you will have to shift down a gear. The two other pedals are your normal break and gas.
Step 2: How to Shift
The first thing you do when downshifting is step all the way down on the clutch. Shift thoroughly so your shift can be smoother when you shift down. Make sure you only downshift if your rpm's are 5,500 or below that way you can get in the power band range.
Step 3: Shifting
Shift to the gear before the one you are on. For our example we are shifting from 3rd gear to 2nd. You have to let go of the gas and press down in the clutch the whole time you are shifting. Once you have the gear you want give it gas and let go of the clutch simultaneously. Try to even it out to where you don't jerk a lot and have a smooth shift.
Step 4: When to Downshift
We went on a hill which was a perfect example for when to downshift. We were trying to get up the hill but our rpm was under the power band so we couldn't make it. We were rolled back as the car started to shake which meant the car was going to stall out. We were in 2nd and we downshifted to first. Our rpm got to the range where they needed to be and the car started getting speed and we made it up the hill. Downshifting makes your rpm higher which increases speed.
Step 5: Finish
All it takes it practice and this skill will benefit you a lot! This is the car we used for our example(s).