It is not necessary to be an expert to prepare a good coffee. We just have to have clear what are the basic concepts to obtain an espresso coffee of quality.
To prepare it we need fine ground coffee, the water should not exceed 90 degrees of temperature and 9 bars pressure. The amount of coffee we must place is 7 grams or rather, the amount required is the one which is just below the nerve of the filter.
The flavour of an espresso coffee also depends on the method of preparation. If we press the ground coffee over the filter, so that it is more compact, its taste will be much stronger because the water will transfer more slowly through the filter up to the cup. If the water flows too fast, it will be because the ground coffee is little compacted and, in consequence, the coffee will be much softer. The opposite can happen: if the water takes too long to come out is because we compact it very much and we could get an espresso with bitter taste and little aroma.