I think what specifically you need to know about largely depends on the field you are working in.
A colleague once told me it is important that you are constantly working on something in your free time that is not something you do at work (eg. different technologies, different programming languages paradigm, different database type, etc).
This simple advice does two things: You are constantly learning, and you are making sure you're looking beyond whatever it is you are doing for money. You are widening your horizon. Maybe you discover something that you can eventually use at work, maybe it will never be useful.. Who knows in which direction we're heading?
A colleague once told me it is important that you are constantly working on something in your free time that is not something you do at work (eg. different technologies, different programming languages paradigm, different database type, etc).
This simple advice does two things: You are constantly learning, and you are making sure you're looking beyond whatever it is you are doing for money. You are widening your horizon. Maybe you discover something that you can eventually use at work, maybe it will never be useful.. Who knows in which direction we're heading?