In order to keep water flowing freely through your drain pipes, keep the following things in mind: Accumulating fats and oils are the main cause for clogs, so never pour fats or other oils down your drains. This includes oils that are not solid at room temperature. If you accidentally spill oils or fats down the drain, run hot water down your drain along with a healthy serving of dishwashing liquid.
The soap will emulsify the fat or oil and move it on down the pipe, preventing a clog.
Get a hair strainer for the bathtub drain. If fats and oils are the main source of clogs in the kitchen, hair is the primary culprit in the bathroom. If you have a strainer, make sure that you remove any accumulated hair from it following each shower. This will reduce the amount of hair that finds its way through the strainer and into your plumbing.
Skip the "Drain Unblocking Liquids" that you can buy at most supermarkets and hardware stores.
Though the acids it contains can help unclog a drain, they also cause significant damage to your plumbing, including premature leaking. This can lead to costly repairs later on.
Your best bet, is to use Coca-Cola. Pour the Coca-Cola in your drain just before you go to sleep, and it should have dissolved the grime overnight. If it hasn't done during a single pour, do it again two or three times. If that does not work, get hold of a plumber then.
If your bathtub or toilet is completely clogged, use a small drain snake – which you can purchase at any hardware outlet – to pull the offending clog to the surface. If your kitchen sink is clogged, try plunging it before trying to snake the drain. If you cannot remove the clog using a drain snake, call a professional.