I have tried most of the renaming utilities mentioned here, but i settled on rename master which combine ease to use interface and powerful renaming features , it has all renaming features, especially i like how text instructions in a way that is very informative and self-explaining, but one feature that i found very useful for me was the ability to import CSV list which i exported from excel as csv file of pre-defined filenames that i prepared earlier and then apply them to my existing list of files, it saved me a lot of time and effort and also it let manipulate strings the i want the filnames to be.
the renaming schemes are easy to figure out even for non-experienced users