In vim, how do I go back to where I was before a search?
Use `` to jump back to the exact position you were in before you searched/jumped, or '' to jump back to the start of the line you were on before you searched/jumped.
Ctrl+O takes me to the previous location. Don't know about location before the search.
Edit: Also, `. will take you to the last change you made.
You really should read :help jumplist it explains all of this very well.
I've always done by it setting a mark.
In command-mode, press m[letter]. For example, ma sets a mark at the current line using a as the mark identifier.
To get back to the mark press ' [letter]. For example, 'a takes you back to the line mark set in step 1. To get back to the column position of the row where you marked the line, use `a (back-tick [letter]).
To see all of the marks that currently set, type :marks.
On a slightly unrelated note, I just discovered another nifty thing about marks.
Let's say you jump to mark b by doing mb. Vim automatically sets the mark ' (that's a single-quote) to be whichever line you were on before jumping to mark b.
That means you can do 'b to jump to that mark, then do '' (2 single-quotes) to jump back to wherever you were before.
I discovered this accidentally using the :marks command, which shows a list of all marks.