Take an easy solved problem you haven't solve, and instead of looking up the solution you try to figure it out yourself. Starting with unsolved problems is too hard in most cases, you need to build up experience with how to tackle the unknown and the best way to do that is to try with known problems that you personally don't know but that you know has a simple solution.
Join a community of learners/practice/excellence and entertain many perspectives, heuristic shortcuts, lens changes, etc.
Try figure it out yourself
Honestly? By applying reasoning. Being wrong and correcting. Not making the same mistakes over and over. Being humble. Not being afraid to fail. Not assuming you know the answers. Stuff like that.