If you take care of your car's mechanical needs yourself, you should check up on several systems regularly.
Under the Hood
Engine Oil and Filter
First up, if your car is from earlier than 2008, you should aim to change your oil and oil filter roughly every three months or 3,000 miles (∼4,800km). Many vehicles made after 2008 can safely make it six months or 5,000-7,000 miles (∼8,000-11,000km).