Part of knowing your value is to occasionally respond to recruiters on LinkedIn and go on interviews. It's good practice anyways, even if you're happy in your job.

Some of the best advice I ever got was to do interviews even if you don't think you'll get the job, or even just for practice. It's like going to the doctor; you just have to go do it sometimes, and it can be surprisingly good long-term.

> Knowing what your employer finds valuable is a difficult proposition

Yes. But you probably have an idea how to reduce the number of headaches for your manager, and how to make him or her look better in front of that person's own manager.

You may go unrecognized for a while be keep doing it because eventually you'll be that person that your manager really doesn't want to loose. That's value.

While I tend to agree if you are going unrecognized and your manager is inept there is a good chance that you are not being seen as valuable to the company and therefore missing #1. That is why I think it is a difficult one. I have also seen the opposite problem though where an employee felt they were providing tons of value and their managers felt the same way, but their peers and other teams found them to be a burden. When that employee left the company there was a bump in productivity and general happiness on many teams. In the end they were providing the wrong things and the value they thought they were providing was actually a deficit. That could be an edge case, but does illustrate that it's not easy to merely make yourself valuable. You must also prove that the value you think you are providing is actual value.

Yes I should have qualified my comment in that I assumed a functional and healthy manager. Optimizing for a dysfunctional one would lead to what you describe.

I would submit that if you don't know what your employer finds valuable, then you're already in a dangerous situation!