There are so many videos and blogs on brewing coffee. Single cup, french press, drip, percolator, Aeropress and on and on. Yes it can be confusing. So I will simplify it for you. It doesn't matter what method you use to brew your coffee, just follow these tips and you'll be on your way to brewing a better cup.
There are three "must haves" in this process; filtered water, a burr grinder, and a means of measuring (weight or volume).
Why must you use filtered water? Imagine a wet sponge. If you try to wipe a wet counter with a wet sponge you will accomplish nothing. The sponge is full of water and cannot absorb more. It needs to be wrung out. Filtering your water is like wringing out the wet sponge. Your water, like the wet sponge, is full of particles (TDS or total dissolved solids). In order for water to absorb the coffee you need to get rid of some of those particles to make room for the coffee. It doesn't require some expensive setup, just use a Brita or similar filter.
Why a burr grinder? There are basically two types of grinders, blade and burr. The blades of a blade grinder look like blender blades or an airplane propeller. When the blade spins it "crushes" the coffee beans leaving course particles and fine particles. Trying to brew different grind sizes is like trying to bake different size chocolate chip cookies in the same oven. Some may be burnt, others under cooked. Also, it is impossible to replicate your grind because you grind by sight. A burr grinder "cuts" the beans to a specific size. Brewing this grind is simple, measurable, and repeatable. A decent burr grinder starts at $150. (They used to start at $500 back in the 90's)
Finally, measuring is very important. In order to replicate your success, you need an accurate way to measure your coffee grounds, water quantity, and water temperature. I use a gram scale for coffee and water and, obviously, a thermometer for water temp.
So here is the overly simplified part. There are four basic variables in the brewing process; water temperature, coffee grind size, quantity of coffee, and the amount of water. Get a pen and paper and track each variable. Change only one at a time (keep it simple). Here is how the variables affect taste:
Too hot = bitter
Too cold = bland (try to keep between 195 and 200 degrees)
Too course = bland
Too fine = bitter
Coffee Dose or Quantity
Too little = bland
Too much = sour (more is not better)
Too much = bland/watery
Not enough = you are wasting coffee (you may get a sweeter cup but less complex/acidic)
These variables work together so, for example, you could get a bitter and under extracted coffee by using too fine a grind and not enough coffee. The cup will be underdeveloped and bitter. This is why you should only change one variable at a time. I generally focus on removing any bitterness before I work with other variables. I suggest anchoring the temperature and water volume thus reducing your issue to two variables, grind size and dose (amount of coffee).
Every coffee is different so, if you want a stellar cup, you'll need to go through this process every time you buy a different coffee. In my opinion, there is no "one way" to brew the perfect cup. Much like "beauty is in the eye of the beholder", taste is what you prefer. The goal is to find a brew you like and be able to replicate it.