Grinders
The first step to getting the perfect grind is to choose the best grinder. There are two types of grinders: Blade and Burr.

Blade Grinders

How They Work
The blade grinder grinds the beans with blades, which can be likened to hacking away at the beans with a knife. This grinder attempts to grind all the beans at once, which results in the lower placed beans being ground too coarse.

Results
Since the flavor is extracted from the outside of the bean, the big chunks resulting from grinding are under-extracted (too weak) and the little chunks resulting from grinding are over-extracted (too strong).

Dos & Dont's
Do make sure to sharpen your blades. (They can wear out).
Do empty all coffee at the end of each grind. Make sure to take a spoon and dig out any hardened coffee, which may have accumulated beneath the blades.
Do make sure to thoroughly clean your grinder after grinding flavoured coffee. The flavours will contaminate your regular beans if not cleaned.
Don’t grind for more than 15 seconds - the blades cause friction, which in turn creates heat that burns the grounds and gives the coffee a bitter taste.
Don’t mix the hardened coffee with your ground coffee as the hardened coffee has been burnt and gives the coffee a bitter taste.

Burr Grinders

How They Work
The burr grinder grinds the beans with revolving discs, which shave the beans into flakes. The discs grind each bean individually and then deposit the grounds into a separate compartment.
Conical Burrs do a better job than flat burrs and are standard on more expensive grinders

Results
The burr grinder produces flakes, which are uniformly extracted. With flakes the flavor is consistent.
Burrs allow you to achieve a uniform grind from Turkish to French Press

Dos & Dont's
Do make sure to thoroughly clean your grinder after grinding flavored coffee so you don't contaminate your regular coffee.
A more lengthy "Dos & Dont's" list is unnecessary as the burr grinder does all the work for you.

If you can afford to spend a few more dollars, the results from a good burr grinder are worth it!