[cosminro]

It takes time and practice. You won't get the practice at work. I dealt with a network flow problem a while back and a spell correction for URLs problem before that. In the last year I haven't done anything algorithmically challenging. Most of the time you're building systems that move data around.

A common mistake is that people learn about complex algorithms and data structures, remember their names but then can't solve questions that involve just basic structures like vectors, stacks or binary search trees.

I can't learn by reading a book, I have to solve problems to really grasp a concept so my advice is this: Do topcoder.com/tc div 2 practice rooms, about 30 of them in a short time span. You'll see the solutions of other people and be able to learn from them. Also the level of div 2 problems is about the level of more difficult interview questions.

Another suggestion is to try projecteuler.net