How to respond to critical feedback. Being able to listen to feedback about your work with an open mind is enormously important, because feedback is one of the most direct ways to get better at what you do. If you respond defensively or shut down, you'll prevent yourself from hearing important information, lose points with your boss and maybe even make it less likely that you'll hear information that could help you in the future. Instead, listen with an open mind and respond with something like, "This is really useful to hear," or "I appreciate you sharing this with me." If you can't stomach those, try, "I want to take some time to think about this, but I appreciate you telling me."
How to negotiate salary when you get a job offer. People sometimes worry that they have to lay out an air-tight case when asking for more money, but it doesn't always have tobe a long speech with evidence about your worth. More often than not, you can simply say "I was hoping you could go up to X amount. Is that possible?" or "Do you have any flexibility on the salary? I was hoping for X."
How to figure out the market rate for your work. This can include asking other people in your field for their opinion, checking with professional organizations in your industry, looking at similar positions on online job boards to see if salary ranges are listed and talking to recruiters in your field - always making sure that you're factoring in your geographic area, which can have a big impact on the numbers.
How to run a meeting. If you lose control of your meetings, let conversation spiral in any direction and don't start or finish on time, people will quickly begin dreading attending any meetings you're running. Instead, always have an agenda, be clear about what outcomes you're aiming for, be willing to redirect the conversation when needed, take your starting and ending times seriously and make sure everyone is clear on next steps before you wrap up. People will be far less likely to "miss seeing" your meeting invites when you do this.