Of course you want affiliates with high commissions, but they should also have a solid reputation with high conversions and low reversal rates (you get $0 if people cancel after signing up). If they’re part of an affiliate marketplace like ShareASale or ClickBank you can see some numbers there. Companies likes Amazon/SiteGround are safe bets, otherwise do your research (or track your affiliate links so you can monitor their performance). Avoid affiliates offering huge commissions since this probably means they’re struggling to acquire/retain customers naturally. This will hurt your numbers (specifically your conversions/reversal rates).
These Associates Program policies (“Program Policies”) are incorporated by reference in the Associates Program Operating Agreement, and capitalized terms used in these Program Policies and not otherwise defined here will have the definitions provided in the Agreement. The rights and obligations of the parties under Sections 3 and 6 of the Associates Program Participation Requirements, Section 3 of the Associates Program IP License and Section 4(d) and 5 of the Associates Program Local Associates Policy will survive the termination of the Agreement. For the avoidance of doubt and without limitation for purposes of Section 6(a) of the Agreement, any violation of the Associates Program Participation Requirements, the Associates Program IP License, Section 1 of the Amazon Influencer Program Policy or Section 3 of the Associates Program Local Associates Policy will be deemed a material breach of the Agreement.
The topic you choose must have enough depth that you can create a lot of content for it. This is important for building an authoritative site, for search engine optimization, and most importantly, for the end user. If you don't have enough content about a topic, you're not going to be taken very seriously as an authority on the topic and it's unlikely you can convince someone to make a purchase from you.