You've gone through an education system that probably never taught you anything about professionalism, logical deconstruction, and comfort with ambiguity. You may have tremendous bookish knowledge, but lacking these three attributes is an immediate invisible red flag that will stop you from getting the job or the promotion you always wanted.

Let's throw some light on the top-5 common mistakes that highlight your lack of these attributes, and what you should be doing instead

• Showing up late without informing your interviewer/coordinator - there are genuine reasons one could be running late, but that needs to be duly communicated ahead of the planned interaction. Inform every marked on an invite, drop a text or give a call, but keep your stakeholders informed. Their time is as much valuable as yours.
• Turning up unprepared for the interview - if you are turning up unprepared, why is it that you are turning up at all? why waste your and interviewer's time? You are better off declining the opportunity, instead of ruining your reputation unnecessarily. You must invest 1 hour to read about the company, the opportunity, some information in the public domain and so on, if you have chosen to show up for an interview. 
• Going silent instead of communicating effectively with your stakeholders - it might come as an insight but everyone knows you would evaluate multiple opportunities before chosing one, everyone knows that your decision might be influenced by your loved ones, and everyone is okay with your being unsure, but nobody likes to be left wondering about what might be happening. So, good, bad or ugly, communicate, communicate and communicate! You'll build more relationships that you ever thought, and you never know, one or more of these relationships may turn gold in the times to come.
• Rambling stuff that does not make sense - let us fill you in on another secret, nobody - not even the most successful individuals can know everything about everything in the world. So, when presented with topics/questions you have no clue about, you got to either draw parallels from what you have expertise on, rationally break down the information you are presented with to come up with simple yet logical answers, or admit you do not know anything about this but can talk about something relevant to the opportunity being discussed in detail.
• Demanding a bomb without a concrete rationale - the whole world is underpaid, friends! who doesn't want more, but that's not how it works. Your next compensation cannot ignore your current and/or previous compensations. If you chose to take a sabbatical, took an opportunity by taking a haircut, or become an entrepreneur that eventually did not work out, you have to make peace with your decision. Nobody else had a say in that! You can definitely demonstrate additional skills/knowledge that you acquired during this period (that surely has a value), but that value isn't the only figure on which your next compensation will be decided on. So, learn about the market standards and try to limit your ask within the broadly acceptable range.