How is your espresso? Are you getting the most flavour from your espresso?
As the coffee starts to flow, you should be getting plenty of rich crema capping the shot of espresso. Fresh coffee will produce plenty quickly.
The coffee will settle, much alike to a mini pint of Guinness. This is why its best to use a shot glass so that you can see the crema forming.
Your shot of coffee will take up to 24 seconds to brew depending upon your blend of coffee.
The crema should stay, the colour should be rich but not too dark and slightly marbled.
Reddish brown indicates the coffee has been over extracted or pale has been under extracted.
Bad espresso can be a result of the grinder needing adjustment to finer or coarser, the tamping being too hard or soft or the coffee machine being faulty.
Experience and experimenting will help you to learn how to get it right to your own taste.