Check to make sure you are using the correct type of bean in your machine. You should use a French or Italian roast espresso bean.
Examine your coffee to make sure it is fresh, ground correctly and gently tamped if you are having trouble creating a "crema" on your drinks.
Clean the steam nozzle and intake hole if you are having trouble creating a milky froth. Make sure you are using cold, skim or low-fat milk.
Check that the filter holder is properly inserted into the brew head if you are experiencing water leaking. Clean any excess coffee grounds from the rim of the holder.
Contact the manufacturer if you are still experiencing problems. Your machine may still be under warranty or the company can recommend a service center.