It is so easy that it's almost impossible to mess up, but there are a couple of things to be careful about. Make sure the heat is not too high and the cream doesn't boil over and never leave it unattended or you will end up with curdled cream.
You can pass it through a fine sieve to eliminate the zest.
You can decorate it with a fruit of your choice, I personally like the forest fruits as they look good on everything.
It is usually served with a shortbread type biscuit for a bit of crunch against the silky smooth cream.