1. A/B test multiple variants of ads
In my opinion, the most valid and effective way to find well performing ads is by conducting A/B tests.
Don't just put 1 ad and hope it will work well. Put several variants of the same ad. Track its click through rate (CTR), put conversion pixel on the target page and track user behavior on it. This is the only valid way I know that will surely show your most converting and money making ads.
2. Test different ad positions and sizes
Image taken from smartinsights.com
According to my experience right sidebar ads get around 0.1% CTR. So you should expect 1-2 clicks per 1000 impressions. If possible, you could test different ad positions, in order to improve CTR. Here is a great resource of average CTR statistics for different ad sizes, positions, and more.
Banner blindness limits your click through rate (CTR)
If it located on the right sidebar people might not notice your ads because of banner blindness.
Image taken from nngroup.com
Users have already developed a resistance to looking at the right sidebar because web admins are trying to get the attention of the users by showing irrelevant and try hard to get your attention ads. Because of that most of the times these ads are ruining the experience.
3. Put relevant ads only
If you put irrelevant ads your user base probably won't be that interested in them. For example, if you have a weight loss site and display job offerings you will probably have no success. Users in this site are looking to lose weight not find a job. Therefore, put ads relevant to your sites niche.
4. Personalize as much as you can.
If you could get some user context or information try to use it so you can show ads specifically made for this type of user group. For instance, users coming from a particular tech site should see only tech job offerings. Bleier and Eisenbeiss, 2015 found that ad personalization improves CTR. More information on display ad personalization here.
Finding effective ads is not easy. Try to test as much as you can until you find profitable ones. Discard bad performing advertisements and concentrate on those that give good CTR and conversion rate.