[truebosko]

If you are in a role where you could be involved in the decision making of the product(s) you work on, getting involved in that [initially informally] is definitely the best way.

Be knowledgeable about metrics/kpis (and help create them if they don't exist), help your teammates grow through coaching, and work your way to be involved in those product discussions.

If you're not in such a position, try looking for a new job. So many companies need product managers and if you come clear on your ambitions, it seems to be easy to get past that initial wall.