Regarding “convincing someone to buy your product is not that easy”, I do agree with you, but at the same time, I remember all those products I’ve bought online. I did not search on Google for those products neither I went to the company websites to get information and buy. They were affiliate people and their blogs that inspired to buy them. PrettyLink Pro, SEO Pressor was recommended by Kimberley, I bought Profits Theme, WP Zon builder because Alex Whaley recommended. Similarly I bought CommentLuv Premium because Ileane, Kavita, Steve and many others were talking good about it.
Yes is the short answer. Any time you are planing on generating money, you should have a plan. No plan means no real focus. There may be some 1/1000 percent of a chance you will succeed, but I haven't met them yet. If you have already started and have generated an income, record how. Doing so will give you material for use in expanding your business faster.
Theme – you don’t need a special theme for affiliate marketing, you probably just need a blog. I recommend StudioPress themes since that’s what Yoast, Matt Cutts (from Google), and I use. Matt Mullenweg, founder of WordPress also recommends them. One of the biggest mistakes I made was using a theme from Themeforest… since they’re built by independent developers who may stop making updates to their theme. This happened to me and I hear horror stories all the time about people having to switch themes and redesign their entire site. I’ve been using the same StudioPress theme (Outreach Pro) for 3 years. Their themes are lightweight (load fast), SEO-friendly via optimized code, secure, and they have a huge selection of plugins for the Genesis Framework and an awesome community in the Genesis WordPress Facebook Group. They include documentation for setting it up and will serve you for many, many years.
Cookie stuffing involves placing an affiliate tracking cookie on a website visitor's computer without their knowledge, which will then generate revenue for the person doing the cookie stuffing. This not only generates fraudulent affiliate sales but also has the potential to overwrite other affiliates' cookies, essentially stealing their legitimately earned commissions.
Be sure to check what kind of customer support you can expect from your affiliate program once you have signed up. Do your research online and if possible, speak to other sellers using the program to get their thoughts. Can you speak to someone via phone or Skype or do you have to wait 72 hours for email responses? Be clear on this because trust me, you will need support at one point or another.