Tips to follow to prevent blackheads are:
Make sure you change your pillowcase every week. If you have oily skin, this is even more important, as the oil from your skin that gets on the pillowcase can contribute to attracting dirt even more. An added bonus of changing pillowcases regularly is lesser chances of hair fall.
Make sure you use a very gentle formula while choosing a face wash. Ideally, you should go for medicated ones that are available at the chemists, rather than over-branded ones claiming to brighten or lighten the skin. These are often too harsh for the sensitive skin of the face and can worsen the problem further.
Use as little makeup as possible. I know that having blackheads, all you want to do is to hide those ugly black spots, but this would further clog them up. What you can do is stick to lighter makeup, the one that lets the skin breathe easy. And always remember to remove all traces of makeup at the end of the day.
It can seem like a good idea to scratch at the blackheads and make them go away temporarily, instead what this does is leave stubborn scars from all the scratching, making the problem more permanent than it actually was before.
Moisturizing can seem like a very bad idea, especially when you already have excessive oil coming out of your skin, but moisturizing after washing the face is as important for oily skin as it is for dry skin to restore the natural pH balance of the skin. Just be sure to use a gel or water-based moisturizer as opposed to an oil-based one.
These are the tips to follow to prevent blackheads.