One thing that helped me was to actually implement things that made use of the "algorithm stuff." Not just practicing in front of a whiteboard, but real executable code!

In particular, anything involving a Tree was never very intuitive until I tried implementing a script to search for files by name. Suddenly both the recursive and the iterative approaches made sense. I understood the trade-offs because they applied directly to my work. That opened the door for more complex algorithms, like a Huffman Coder (which I wrote in C, as part of a CS class).

The other thing that helps me in interviews is to just talk through everything I am thinking. It feels like I'm stating the obvious over and over, but a good interviewer will be able to follow your thought patterns and help you along when you get stuck. Also it just helps to hear yourself say things outloud sometimes. If you just stand there silently decoding a problem in your head, the interviewer can't help you and has no idea how you'd approach a real problem on the job.