I'll post my 2 cents here since I suspect my experience will replicate many of those already stated in the 53 page leopard wrasse primer. Hopefully it will help since I've had both failure and success with leopard wrasses.
I've lost a couple of ornate wrasses within a couple of days. Had a Potters wrasse do well for six months and then inexplicably die despite feeding well up until it's last day or two. Currently I have a Meleagris species leopard wrasse who has done well for about a year.
I have purchased all of the wrasses at my LFS. I acclimate them for about 45min and then place them directly into my display tank which has 1-3 inches of live sand depending on the location. The key for me was to observe them at the LFS- the longer, the better. If it's survived over a week at the LFS before I buy it, that's a start. The most important factor in my experience is how they're eating at the LFS. The Potters and Meleagris that i've had success with, fed voraciously, entered right into the mix with other fish to eat frozen food such as mysis at the both the LFS and subsequently in my aquarium. Those that didn't do well were more reserved and might only pick at food placed right in front of them. It sounds from your posts that you may not have the option of a LFS as many of yours were purchased via the internet, in which case i'm not helping much...
Another reason i thought i'd share the above, is because it really may not be rocket science or require a PhD in icthyology because based on many of the posts there are a lot of experienced aquarists with perfect parameters and plenty of live rock who still struggle to keep leopard wrasses. I don't consider myself an expert, nor are my water parameters perfect, but sometimes it's just getting the right fish, one that acclimates easily and feeds well.
Which brings me to a couple of tag on questions- can you quarantine sand dwelling fish in a bare bottomed QT (I personally haven't but do then worry about bringing in disease into an established tank)? And do small, younger fish acclimate better?