The fundamentals of brewing coffee are straight forward. We complicate things a little too much sometimes. Keep the following things in mind and you're on your way to a great brew.
Water is a big factor...
Water represents around 90 percent of your brew. In fact, you're drinking delicious flavoured water. I don't want to get too geeky and explain water chemistry, but to create the perfect cup, your water needs to be the best it can be.
First, if the water doesn't taste right, don't use it. It's pretty simple.
As a rule, bottled spring water or a good filtration system are your best bets. I use filtered water from my Brita filter jug. Brita filters are an easy and cheap way to get great quality water both for brewing coffee and drinking. I did an experiment comparing Melbourne tap water to tap water filtered through my Brita filter jug. The results where based on taste. The Brita filter produced a sweeter and more acidic cup.
Second, for most brewing methods, I recommend heating your water to 92-96 degree celsius for the best flavour extraction. Using a thermometer to measure the temperature is definitely the best way to go. If you haven't got a thermometer, allow your kettle to get to boiling temperature and then let it rest for 30-45 seconds.
To keep your coffee fresh, it's best to grind your coffee only when you need to use it. Grind it when you're ready to start brewing. There are many grinders on the market: from the trusty hand grinder to the fully automatic versions. I suggest you try and get a burr grinder. Burr grinders are great because they produce are very even grind size.
I adjust the grind size for each brewing method. I write my brewing guides the way I like to brew, but it's definitely something you can adjust to suit your taste. It's good to experiment with grind and dose size. For example, try a higher dose with a coarser grind or a finer grind with a smaller dose.
When you're brewing for filter, use beans with a lighter roast profile (rather than an espresso roast profile). Lighter roasts perform better in the cup when brewing filter coffee. They are sweeter and have a lot more clarity. If roasted well, you will find that the flavour profile is true to the origin characteristics. For example, Ethiopian coffees should be bright, very floral and have high acidity.
Pay attention to the roast date on the bag. I think consuming filter roasts between 2 to 8 days is optimum. You will lose some of those subtle flavours in your brew if your coffee gets older.
You should clean your brewing equipment after every use. If you leave your equipment dirty for a long period of time, coffee oils tend to leave a rancid smell. The easiest way to clean your equipment is straight after each use in hot water. Cleaning solutions can be used, but be sure to rinse throughly. You don't want a soapy taste in your next brew.