First...good for you for reading this!  We're going to make this easy and the payoff in terms of the taste of your coffee is going to be night vs day!

The coffee brewing process can be complex and there are plenty of variables to learn about later.  Let's appreciate the complexity, but not drown in it

We're going to explain the basics of brewing so that you can make a flavorful and delicious cup of coffee every single time.

The one term you do need to understand: Extraction

It's simple...there are soluble compounds inside the coffee that impart flavor and body. Hot water will "pull out" or extract those flavors...and that's brewing!

If you're experiencing poor tasting coffee is most likely because it was either under-extracted or over-extracted during brewing 

Under-extracted:  Your coffee is lacking flavor, it's tea-like, or sour

Over-extracted:  Your coffee is tasting too bitter or a general unpleasant taste

Ideal extraction:  Balanced sweetness and body, complex and delicious...brewing perfection!

Note:  Old, stale coffee will produce a bad taste no matter how good you brew it, so let's assume you are buying fresh roasted coffee :)  

The simplest way to adjust your extraction is to adjust the grind size of your coffee  

Think about water flowing through a funnel that is filled with sand.

Fine sand will be more compact and it will take a longer time for water to flow through = increased extraction

Coarse sand will be loose and porous and water will flow through faster = decreased extraction

So let's think about it by answering this common question...

Q:  I have an auto-drip brewer and therefore can't control the flow of water, so how do I increase or decrease extraction?  

Although you can't control the flow rate of water over the grinds with an Auto-drip, you can still adjust extraction by adjusting the coffee grind size.

If your coffee is tasting under extracted...grind finer and the water will take longer to flow through, thus increasing extraction.

If your coffee is tasting over extracted...grind coarser and the water will flow through faster, thus decreasing extraction.  

Here's a chart showing the range of grind sizes and the best brew methods for each:

Bottom Line:  If your coffee is tasting just blah and you're not experiencing its full flavor...experiment with different grind sizes. 

Move in the direction of grinding finer until your coffee starts to taste a little  bitter (over extracted), THEN go back up one level coarser and that's the ideal grind size. 

Congratulations you have just leveled up!