Every family in Italy owns one of these machines. Here are a few tips:
1. In Italy this is NOT called an espresso machine, but a Moka machine. An espresso is what you would drink in bar made with a steam or high pressure machine with the crema on top.
2. Smaller size Moka machine tend to make better coffee.
3. Never wash the Moka with detergents, just rinse it under tap water
4. You've gotta use it often for a good coffee.
5. If you haven't use it in a while, make a weak coffee ("lungo") and discard
6. DO NOT put the MOka in the dishwasher.
7. Use drinking water. Avoid tap water especially if very chlorinated
8. Never compress the coffee.
9. For a strong coffee fill the filter with ground coffee and make a small cupola that slightly protrudes beyond the rim. Do not press down.
10. For best coffee, heat at very low heat. It's ok if it takes 10min.
11. As soon as coffee reaches the top, remove from heat
12. Do not let the coffee boil
13. Use good quality coffee, not too strong, medium grind (try Illy for a good commercial brand)
14. Sip while still hot, enjoy!
15. (Added Nov 2012) - Wait until all the water has reached the upper chamber before removing from the heat. You will be able to tell by the sound (takes some practice) or simply visually. As soon as no more coffee reaches the upper chamber remove from heat. Do note let the coffee boil. With practice, you may remove from the heat even sooner, by just using the residual heat in the lower chamber.
16. (Added Nov 2012) - Some times you may put too much coffee, or the coffee is too finely ground, or it's been packed too hard. In all of these situations, the end results is typically that the coffee struggles reaching the upper chamber. You can tell by the spouting noise occurring too early, the foam occurring too early, and how slow the whole process is. You can try increasing the heat if that helps. However, you will likely end up with a coffee that is too bitter and tastes burned. Back in the old days, this was dangerous business with many machines exploding (they had no safety valves). Regardless, your coffee is ruined and I would suggest removing it frmo the heat immediately, let it coold down and starts all over.
17. (Added Nov 2012) - What kind of coffee should I use? Experiment, experiment, experiment! Here are some tips I have learned by experimenting. Until you become confortable with the operations of the machine, you can use a good commercial brand like Illy (although it's quite expensive). I wouldn't want you to blame the machine, just because you happened to use a bad coffee. Then start trying different varieties from different roasters. If there are independent roasters near you, why not giving them a try? I haven't had good experience with roasts marketed towards Espresso machines (I find the roast too excessive). Try to buy whole beans and grind them yourself. I find the cheap and popular brands pretty bad for Mokas, even if they happen to make good American style brews. I have had pretty good luck with small roasters and Colombian varieties (or Costa Rican). I have also had outstanding African coffees (Ethiopian). Unfortunately, I found they are seldom consistent.