When to permute two times to find optical configuration
If you switch any two substituents, that will change the stereochemistry. If you do a second switch (any two), you are back to the original stereochemistry. You can try it out with substituent 4 in the back, and seeing what switching around 1, 2, and 3 do to the clockwise or counterclockwise orientation (i.e. whether it is R or S).

Two switches (for example switching 2 and 4 and then switching 3 and 2, see animated GIF) amounts to a rotation around the bond of the "unswitched substituent (here substituent 1). This does not change the stereochemistry.

If you are spatially gifted, you can just do the rotation in your head to get substituent 4 in the back. If not, you can do one switch (realizing you just interchanged R and S) or two switches (R stays R, and S stays S). It is personal preference (oops, I think I just said the question should be closed because the answer is opinion-based).

If you want to try it with 3D models yourself, check out http://proteopedia.org/wiki/index.php/R/S_nomenclature.