What are the common mistakes in Affiliate Marketing?

The most logical way to approach this question is to start with what you SHOULD do and regress from there…

Fail to provide value to your customers and to those whose products you advocate;
Lie;
Fail to start building your own email list ASAP – social media algorithms and search rankings can change on you overnight – so don’t make yourself dependent upon them;
Fail to understand what you are promoting;
Fail to niche down small enough and target your promotions appropriately – do not spread yourself too thin;
Promote in a niche in which there is insufficient interest or profit;
Be impatient – it takes time and effort to provide enough value to potential customers without compensation, to establish a reputation of honesty, to build trust;
Fail to do your homework to understand how to build your own infrastructure or hire it out to a reliable partner;
Publishing poor quality content – too wordy, too non-specific, not focused enough – after all, potential customers rely on you to summarize what they need to know to make a good decision, so be concise and truthful;
Misapplying affiliate links on social media – understand the policy of whatever platform you are using, and follow their rules – remember, it all starts with building trust among your potential customers – and the purveyors of social media sites will terminate you for cause, or just because if their algorithms change – hence the value of your own list;
Fail to understand and properly utilize SEO or partner with someone who does – I work with an experienced Internet marketer – if you want to DIY, check out Miles Beckler’s YouTube tutorials;
Being too pushy – build the trust, build the list, offer the product only after and make it valuable to your potential customer;
Promoting crap (unless your niche is organic manures);
Paying for ads in an undisciplined and poorly researched way – you can get into trouble fast, so work with a pro in the beginning, until you understand all about doing your own research;
Failing to focus on a niche, message, quality, customer experience, value;
Failing to track your results and adapting your strategy accordingly.