The most typical solution is to put use Google Adsense. It is ridiculously easy to set up, and you can start generating revenue right away. In theory. The problem is, Google Adsense, as well as other ad services like it, really aren't going to make you a whole lot of money, in most cases.
As an example, I have one website that I have ads on. I got 1,000,000 page loads on that site last year, and I brought in about $400 for the entire year on ads. If your site is just starting, you'll have far fewer page loads, and so far less money as well.
Your other solution is to put a little thing on your site saying "You ad here!" Sell directly to the advertiser, for a fixed price per month. It sounds like that's where you're headed eventually.
You'll always get better payment from something like that, though you'll have to manage the payments and getting the ads from them and everything. You might be able to get as much as 10x as much revenue from that, which in my case, might take me up to $4000 for the full year. It's still not a lot of money.
Of course, people only want to pay to place their ads in a place where people will actually see it, and if you only have a handful of visitors, no one will want to pay for it.
In fact, there are very few examples of companies who actually are able to survive solely off of ads.
I'm not trying to discourage you, but I just want to point out that if your entire business model is "Make a website, put ads on it, and profit!" you probably won't be successful. It's a nice way to make up for some of the costs of hosting, and things like that, but contrary to what some folks on the Internet tell you, it's tough to really use this as your only revenue stream and expect to support a business with it.
Go ahead and do ads. Start with Adsense, because it is simple and automatic. Later on you can switch to working with the advertisers directly. But also find other ways to bring in money for your business, because ads probably won't be enough.