Fundamentally the main dilemma with coffee is extraction. For barista this is well known. But for the consumer; Extraction has a few very important components.
Firstly, the coffee machine, especially at the head (where the coffee comes out), has to be set at the right temperature. This is a little understood part of the making process. Now its not a difficult thing to grasp, but unfortunately as most """barista""" aren't taught anything about machine settings, this sadly goes unchecked and isn't regarded as highly as is necessary.
Once the temps have been adjusted appropriately; We move on to the grinder. There are a huge range of these and it (again) generally is little understood how important they are. I think for any begginer a "MAZZER - Super Jolly" or "DIAMOND - K6" give you a good start. Reasons being; Solid performer, reliable, good technology, proven to handle a heavy-ish workload. DO NOT buy a step ginder, this is the type where you have to press down a button to adjust the grind settings. BAD SYSTEM, not enough control. Micro adjustment grinders are the ones. Anyway a good grinder is very important.
Now to Bean - Whats important is to like the bean you are using. Cause there are soooooo many different ones. There is no right or wrong with region or organic or fair trade. What it comes down to is quality. If your ethics are swayed toward making specific choices, so be it. But make sure the quality is there. OK, from a proffessional point of view, freshness is vital. 72 hours - 10 days after roasting is the optimum window of perfection. Some say its smaller, some wider. But this is a good range to aim for. Anything over 14 days really shouldn't be put through any bean lovers machine. But for the less concerned, its up to you how bad you like your coffee to taste.
Tampers - All I'll say is make sure its comfortable to use and the right size for the group handle (the bit you put the coffee) you're using. My suggestion is not to use the small, really heavy stainless ones. They're hard to hold correctly while applying pressure to the puck (coffee in porterfilter/group handle)
Dose and grind - This is a very controversial and broad debate. Though essentially its a fairly basic formula. Big dose - Course grind. Small dose - Fine grind. Medium dose - Medium grind. But....There are a few who like to extract a dripping pour, which gives high level sweetness and body. But is prone to bitterness if incorrectly dosed. Also it tends to lose flavour as you get to the bottom of a milky brew. I suggest this extraction for hardend espresso drinkers.
Along side and vital to the dose and grind, is the Tamp - Again a very personal approach. I personally tamp at approx. 15kg. Now this isn't the gods word on tamping, but in my opinion soft tamping is unreliable and inconsistant. I'll write more on tamping another time
When the coffee is pouring, its preferrable to see a warm, honey-like stream. If the coffee is super fresh, this may be hard to achieve. you can either up-dose or simply be ok with the taste you get. I think avoid making the grind too tight to get the right pour. Find out off your supplier how fresh the bean is.
Thats all for now, feel free to reply, I encourage it....