There are several lesser considered factors when brewing at home that can significantly improve the flavour of coffee. Things like water quality, coffee storage, and machine maintainance should all be considered when brewing at home (most of us dont have those cafe quality machines so every detail counts!).
Water Quality
Firstly, lets talk about water. Interestingly enough, the ideal coffee brewing water is not bottled or distilled. This is because it isnt about impurities as much as it's about hardness and PH. Ideally, you want to be using hard water; or in other words, water with a high mineral content. The minerals present in hard water actually help to extract flavour from the coffee grounds. Because of this requirement for mineral content, tap water is in fact the best option! Unfortunately however, tap water is notorious for containing chlorine and other impurities which can taint the flavour of your coffee. So, the perfect combination is tap water and a good water filter. There are plenty of different types of tap filters (jug or built in); just make sure you get one that doesn totally get rid of the good minerals! Most cafes that know their stuff use reverse osmosis filters. These filters have a higher price point but are a great investment if you are serious about coffee (and just want great tasting, clean water!).
So, why not bottled? There are the obvious implications of waste when we talk about bottled; but the issue when brewing is that bottled water tends to be either very dense in mineral content or lacking altogether. Super soft water on the other hand such as distilled water has everything stripped out and is also more acidic (strange but true).
The Beans
Next lets talk about the beans themselves. Number one is storage - invest in a quality, opaque airtight storage container for your beans and store them in a cool, dark place. Outside factors such as sunlight, extreme temperatures and air exposure speed up the rate of ageing (as with most foods) and lead to a loss of flavour and depth.
Buy whole bean! Ground coffee loses flavour extremely quickly. Grinding your coffee just before brewing is the ideal way to get all you can from your beans. There are tons of grinder options for all budgets - and even if you get a cheap one, your coffee will taste better than buying pre-ground (we promise). Additionaly, try to buy only what you need, as you should try to cosume coffee within two weeks of opening to avoid drinking flat, stale coffee.
Whether you are buying preground or grinding beans yourself, make sure the grind size is suitable for your brewing method. This is absolutely crucial. Grind size is so sensitive that most cafes test and tweak grinder settings sometimes multiple times a day to ensure consistency. So, you can imagine that using ground beans for a cafetiere in your espresso machine isnt a good idea. On a related note - consider the type of coffee you buy related to the brewing method. For example, french press or pour over do not come into contact with grounds in the same way that espresso does, so opt for a coffee with more light, fruity notes. On the other hand, if you have an espresso machine you may choose a darker roast with chocolatey, nutty notes. There are no rules about which types of coffee can be used with what brewing method, but if you arent impressed with your morning cup it may come down to the combination of the two.
Maintenance
Finally, clean your equipment regularly regardless of what you use. Fine coffee particles can quickly build up and effect the flavour of your brew. Additionally, hard water can cause mineral buildup (limescale). Vinegar and bicarbonate of soda are effective and safe cleaning agents; otherwise there are quite a few specialised coffee machine cleaning products on the market.