Take advantage of marketing tools whenever possible. Many affiliate programs offer useful resources to their affiliates aimed at helping affiliates make more sales. These range from monthly newsletters highlighting upcoming sales, tips or affiliate case studies, Facebook Groups just for affiliates, private webinars explaining marketing strategies in depth and more. Ultimate Bundles does this exceptionally well.
Affiliate marketing is also called "performance marketing", in reference to how sales employees are typically being compensated. Such employees are typically paid a commission for each sale they close, and sometimes are paid performance incentives for exceeding objectives. Affiliates are not employed by the advertiser whose products or services they promote, but the compensation models applied to affiliate marketing are very similar to the ones used for people in the advertisers' internal sales department.