It's good to choose a Daily cash siphon merchant who has great marketing skills. These type of merchants always launch good products and really know how to sell and what to sell. They know what the buyers want which makes much less work for you and having to convince the buyers to buy.
The key to success in affiliate marketing is selecting the right niche. Always choose the market that has the high demand products and don't be afraid of high priced items. Definitely avoid the free markets where users are offered the free trial products. In these cases people usually don't come back to purchase the real product. You should offer a range of different products that are in high demand with different price ranges.