Finding advertisers can earn you affiliate commissions. This is nothing new and has been around as long as the internet itself. If you refer an advertiser to an advertising medium you make a percentage of whatever the advertiser spends, or you can get advertising credit for your own ads.

I used several methods for advertising with mixed results. Generally speaking people are tired of reading advertisements so most are 'blind' to internet advertisements. They look around banners and delete any ads in their email box, if they weren't removed already by a filter.

So the Click-Through-Rate (CTR) varies per method and your advertisement specifics but usually it is pretty low. If you can get a CTR of 1% you're doing real good. That means that for every 100 ads you send out, 1 person takes a look at it.

With that said it is obvious that advertising is a numbers game. The more exposure your ad gets, the more readers it will get.

Sending out ads on the internet can be done in several ways. Here are a couple:

1) Have your ad posted in electronic magazines (eZines). You probably saw the advertisements; have you ad sent to 300,000 eZine readers for a $xx. My experience is that this type of advertising isn't worth the money. What you could consider is sign up free for a eZine co-op and just for becoming a reader (member) you get to place a free ad in each of the eZines in that co-op. Be aware that your ad is hidden somewhere in the eZine email. Most 'readers' will never see it.

2) Join safelists. A safelist is a list of people that volunteer to receive emails from the other members, and they get to send theirs to that group. Since most people join safelists so they can send ads, don't expect a lot of those people reading yours. In general the CTR of safelists ads is pretty low. 

3) Have your ad emailed directly to readers of eZines or safelists. These so called solo ads usually work best but even then don't expect a lot of response.

No matter wich method you choose, always use a separate email address to subscribe to safelists and eZines. You don't want ads from eZines and safelists in your regular email box. I recommend you setup a free Gmail account for this type of subscriptions. Gmail allows you to create filters that allow you to discard email from certain sources immediately. They won't even reach your inbox. This is great if you want to keep your inbox tidy.

If you have something to advertise, advertise it everywhere you can. More exposure means more readers and thus more sales. I prefer the free methods because paid options are in my opinion not worth the money you spend on it, although it does depend on your product/advertisement of course.