This is not a thing that can be answered briefly, other than with 'Practice.'
Some things to try as practice;
Implement a sort in your favorite memory managed language (java, ruby, go, whatever)
Now do it in C.
Now do a harder sort, both ways.
Now find a paper explaining an algorithm you think is neat. Implement the paper in both languages.
Now do a linked list or other data structure, both ways.
Do a harder data structure, like maybe a hash.
Do all of an algorithms textbook, both ways
Get a job at a company doing search/storage/distributed systems work. Worm your way onto the teams writing the underpinnings (this part is the hardest thing I have suggested.) Fix bugs, write a feature.
As above but for an appropriate OSS project.
Did all that? Congrats, you're well on way! (I am not an algorithms master nor an authority on the subject, but I know folks i'd describe that way and this is how they did it, roughly. College helps, unless you're like me and it makes everything harder for some reason)