I have been trying a lot of PPC (pay-per-click) advertising lately. Even on my websites that are only monetized with contextual ads have done well.
I only recommend working with well-known companies such as Google AdWords, Yahoo Search Marketing, or Microsoft AdCenter.
If you make the minimum bids on long-tail keywords, you can get PPC traffic that costs you $0.10 per click or even less.
The traffic is pretty good quality.
If your website is monetized well enough, you will make a profit. For example, if you pay $0.10 per click, then you will make a profit as long as you make more than $0.10 per visitor on average.
Having a great website will be easier to monetize well. If it is a good, useful website, then the visitors will tend to stay for longer, they will come back, and they will spread the word about your website. That will give you more page-views for each click you buy which will lead to you being able to make more money, whether you are publishing ads or selling products of your own.
If you are not making more than $0.10 per visitor on average, then try to monetize your website better. You can monetize it better by creating a new product to sell, by publishing more ads or different ads, and by making your website better.