One great thing about vim is how you can search/replace with just a few keystrokes. Being able to search and replace at light speed makes you feel very wizardly. Here are some commands I've been using frequently to do so.
(Note that these are all regexes, and furthermore vim regexes, which differ slightly from other regex implementations, and I won't get into that.)
(just type this, in insert mode, and you're instantly at the next instance of "foo". Then hit "n" to go to the next instance of "foo".)
same as the above, but case insensitive. (I guess you could do :set ic first instead of the \c there, but I don't like doing things that leave state lying around if I don't have to)
Replace all "foo"s with "bar" on this line only.
Replace all "foo"s with "bar" in the entire file.
Replace all "foo"s with "bar in the whole file, but ask for confirmation at each one. I like this one a lot.