Dump any grease after cooking into the trash rather than down the garbage disposal of your sink.
Don't flush napkins, tissues or other solid materials down the toilet. Toilets are primarily designed to flush fecal matter and small amounts of toilet paper at once. Adding more to this can cause blockage in sewage pipes.
Call the customer service section of your department of public works or your utility company if you notice that you are losing pressure in the supply or your drains are slow to flush solid materials. If they cannot help you, then contact a plumber. Low pressure and slow flushing is a sign of low sewage flow, and the drains will need to be cleaned of debris by a professional.