You may find that the writing from right to left is sometimes called "retrograde". It is thought the retrograde form of writing preceded the boustrephedon, which, in turn, preceded the left to right or so-called normal form.
Added after an email correspondence: I selected the accompanying graphic to show the traditional boustrephedon and the mirrored form. You don't need to know Greek to see that the form of the letters face one way in one line, the opposite way in the next, and a third way in the third. Even if you do read Greek, many of the archaic letter forms (like the circle with the cross in it for theta and the H with two extra horizontals) may puzzle you. The point is to see the directions, not to present you with a text to translate. I'm sorry if this is frustrating.
A Visual Trick
The Greek form called stoichedon refers to writing in a line that is aligned vertically and horizontally*. The Latin SATOR square [ROTAS OPERA TENET AREPO SATOR] is an example of this careful spacing and reads as valid words (if we accept the hapax legomenon of Arepo as someone's name) backwards and forwards, up and down:.
ROTAS
OPERA
TENET
AREPO
SATOR
For an interesting look at early inscriptions see this early 20th century article:
"On Dating Early Attic Inscriptions"
Leila Clement Spaulding
American Journal of Archaeology, Vol. 10, No. 4 (Oct. - Dec., 1906), pp. 394-404
*For more on the horizontal mirroring of text, see:
"Further Comments on Archaic Greek Inscriptions"
L. H. Jeffery
The Annual of the British School at Athens, Vol. 50, (1955), pp. 67-84
There it says: "All is written 1. to r. in ' false boustrophed'o-ni.e ., one line continues by a hairpin bend into the next, so that the letters continue to run 1. to r., and the alternate lines are upside-down, if the document is held horizontally."
