There are many ways in which you can monetize your website, the most common is to use Google adsense. This is a pay per click company so the aim is to generate as much traffic as you can and if someone was to click an advertisement you will get paid. They often have great payouts on a monthly basis direct to your bank account or by cheque.
You have to make sure you follow their terms and conditions very carefully as you are only allowed one account per person, if you get banned your sites will be blacklisted making them hard to sell in the future. If you follow them you will have no problem and always be sure to report any unusual activity to Google.
Although it is very tempting you must never click your own advertisements or ask anyone else to click them hoping Google won’t notice. They will notice when they come to reviewing your account before you reach the $100 threshold and your account will be terminated and any earnings will be returned to the rightful owners (Google AdWords advertisers). This means you will have wasted all your time and effort into making the website and cut out a vital stream of income.
Be sure to do your research to ensure that the payment per click is reasonable as for niches such as gaming its really low compared to niches such as finance and mortgages. The big mistake that many people do is to chase the high paying keywords, these niches are too saturated so the competition is really hard. You are best trying to find an undeveloped niche in which you can take full advantage of.
You can tweak your website in order to get the maximum potential out of it by moving your advertisements around to find the best layout. There is a hotspot image in the Google AdSense website which will give you a good idea where the average browser will look and click. Place your ads in there and hopefully you will see the return.
Once you have found the best layout for your site through trial and error you need to get ranked high for your keywords to bring in huge amounts of traffic hopefully converting into a click.