You should regularly check your tire pressure. As a rule of thumb, at least once a month. The appropriate operating pressure for you can be found in the manual of your specific bicycle model. It depends on your weight, riding style, and tire size. Heavier riders should inflate a bit more, while lighter ones can pump a bit less. You should also clean and oil the chain occasionally. Remember: less is more! Excess oil will only spread on the bike and its surroundings without providing any additional benefits.
Lastly, you can check the brake pads and regularly tighten the screws. Please refer to the torque table in the manual of your bicycle model.