Depends on the type of knit of merino - if its felted then I wouldn't worry. If its interlock it will be exactly the same on both sides, same with ribbed. Otherwise there should be a "knit" and a "purl" side = if you knit you will know what that looks like, otherwise if you don't knit, the knit side will look like rows of v where the purl side will be more like, um...rounded w or n's. The knit side is the right side, and the purl is the wrong side.
A sewing friend also told me I think that the cut edge will roll towards the right side, and away from the wrong side (ie. if the cut is perpendicular to the grain, not parallel to the selvedge (sp?)).
DS 12yrs, DD 9yrs, and DS 6....