You keep a close eye on all the key numbers and metrics of your sales funnel because that's the real measure of the impact you're creating.
However, your decisions should also depend on the type of audience you’re targeting: If you’re targeting businesses, then you should focus on high-paying, low-volume programs. You can make a much bigger profit this way because your target market isn’t that large but they’re willing to spend more money on the product and services they needIf on the other hand, you’re targeting consumers, then you should focus on low-paying, high-volume programs; that’s because consumers have less money to spend but at the same time, your audience pool is much larger which means you’ll be able to sell high volumes of those products or services

As a beginner affiliate marketer, you need to carefully study the minimum sign up criteria of the program you want to join.
If you try to sell a product that is in low demand then chances are that you are not going to get many sales no matter how hard you try. So it is a good idea to spend a bit of time researching and finding out if a product that you are thinking of promoting is a product that your audience needs. If your site gets decent traffic then you can conduct an online survey and easily get input from your visitors.