A car's transmission is a vital part of its operation, as the transmission obviously determines the direction in which you drive, and it also keeps the car safely in place when you're not driving! Repairing and replacing a transmission can be very expensive, which is why it's good to protect that transmission as much as possible, and prevent any early or unnecessary repairs. Note how you can you can protect your vehicle's transmission, and a few signs that might signal that it's failing and needs fixing.
A transmission or gearbox is made of up separate clutch plates, each sitting next to each other. Shifting the transmission results in extreme pressure on each plate as they slide into gear. This friction, and the friction created as the car moves forward or backward, causes those plates to eventually wear down.
It's good to avoid unnecessary friction against the plates by ensuring that your car's transmission fluid is always in good condition; have the transmission flushed and drained as often as recommended in the vehicle's owner's manual and even more often if you often haul anything behind the car, as this causes more pressure on the transmission. Be sure you use the right type of fluid for your vehicle in particular, as the wrong fluid might be too thick or thin to adequately protect your car's transmission.
You might also add an auxiliary cooler to the transmission, as keeping the plates cool as you change gears can reduce this friction. This can be especially good if you tow something behind the vehicle. Excessive grinding and a "sticky" or slow response when you put the car in gear often means that there is too much friction against those plates, and the transmission then needs repair.
It's never good to "slam" your car between gears, meaning to shift while the engine is revving. This also causes excessive friction and wear on the gears, and the chains and other pieces that fit the clutch plates may be more likely to snap or not mesh properly with the teeth of those plates.
If you're looking to add power or more pickup to your car, you might install a turbo booster or custom exhaust, or otherwise upgrade the engine, but don't rev the vehicle's engine and then push into gear from a full stop. If you notice the engine hesitating when you do shift it into gear, this often means those plates or chains are worn and need replacing.
For more information on transmission and gearbox repairs, contact a local mechanic.