How to force choosing commission by product ID

If you want to generate commissions only for the certain products of your site, it is possible. You can force the generating commission only for defined products with specifying product ID's in the campaign. The sale with product ID not defined in any campaign will not be saved.
NOTE: Do not use the same product id in more campaigns, because in this case the system would not assign the sale to the default campaign, which would result in not saving the transaction or saving it to the random campaign of the particular product id (the one was used in more campaigns). 

This configuration can be found in Configuration > Tracking settings > Tracking levels 

Check an option Stop tracking if product is not found in any campaign. When this option is check, sale will be saved only when product ID is found in some campaign. Sales without product ID or with Unknown product ID won't be saved.
NOTE: If you want to save sales without the product ID, you can also check option Do not stop, but save to default campaign. In that case sales without product ID or with Unknown product ID will be saved into default campaign.
When you set this, donĀ“t forget to enter the matching product IDs for your campaigns at Campaigns > Campaign Manager > Edit campaign > Product ID matching