The most consistent weight readings come from weighing yourself naked, so differences in the weight of clothing and jewelry doesn't impact the scale. By the same token, you can't strip down at a WW meeting, so the objective would simply to wear similar clothing at each weigh-in. I remember a case where someone regularly weighed in in his shoes -- he did it the same each week, so that he wouldn't magically "lose" a few pounds one week. (Some folks complained that his shoes were messing up the top of the scale... you get the idea...)
Incidently, weight ranges are often quoted as "in light clothing" -- from what I have seen of clinical procedures, there is an effort to ensure that folks aren't wearing heavy sweaters, heavy pants or skirts, etc. -- that they truly are wearing the lightest clothing possible.
