1. Likeability counts for more than "job skills"

People want to work with someone who they enjoy working with. Job skills can be learned, but an unlikable person will tend to stay unlikable. Likability only gets more and more important as you move up the ranks- as a manager, you get to delegate most work that requires job skills you don't have, but be a jerk, and you'll find yourself with huge morale and turnover problems. Social skills, more than anything else, are what make people rise through the ranks.

I recently started a new job which listed a requirement of 5-7 years' industry experience. I had zero. They hired me because they liked me more.

2. Don't be too loyal

A recent study showed that the people who make the most money are those who switch companies every two years. You can find it on Forbes. Most people get too comfortable in their jobs and coast for too long, receiving small, incremental raises. But you can often make bigger jumps by switching companies, especially if you're good at the skill of job hunting.

I want to put a couple caveats here. I think the study focused more on the younger crowd- switching jobs every 2 years will catch up with you after a decade or so. You should be able to show that you've received a promotion within your company at least once in your life. Also, learn how to engineer promotions- find needs your company has, and volunteer to fill those needs. Start adding value for your company. Then ask for a better job title and more money, if it hasn't been offered to you already.

3. Don't be better- just be different

In my previous example, I got a job that required 5-7 years experience, and I had zero. Other applicants had 5-7, and I think some might have had more.
Aside from being more likable, I was unique- I talked about stuff like doing kung-fu on my profile, came from a very different background than the other applicants, and took the interview in a different direction than the other applicants.

Would it be even better if I had more experience and wasn't so under-qualified? Sure, up to a point. A couple years' experience would be fine. But if I had 5-7 years, I'd be overqualified. At that point, I should be aiming higher. If you're "better" than all of your competitors, they shouldn't even be your competitors- you should be working at a higher level than them, using uniqueness to beat better-qualified competitors.