The devil is in the water. Assuming you can get the grinds right and your brewer gets up to temperature, the one last issue is what water you use. I can almost certainly tell when someone has hard water by the description they give on the flavors of certain coffees. Water is too soft, same deal.
In a pinch, I use Poland Spring but it is a bit too soft and flat for coffee. It brings roast notes to the front and just seems thin in most brews. I like Eternal if you must get a bottled water. It can be found at whole foods and will bring a lot of flavors to the front in a round and sweet manner. Sometimes we run across people with harder water and they seem to have no roast notes while acidity jumps out of the coffees and the brew is not extracting or developing. The trick is getting everyone to see and taste what we are tasting at the shop.
At home, we recommend Brita Pitchers or the Zero pitcher when you don't have a good clean source.
The point is, use clean filtered water. Most areas have a local water quality monitoring system and you can send in samples for free and get results. In the past, we have contacted the Cambridge Water Operations Division and gotten info on the water supply. I highly encourage anyone to take a look at what's in their water.
