I've made 3-sockets just recently (I've made more in the past but not with this method) by using MB's. I've bought MB's at around 25 minutes after the hour. Opened them all roughly 5 seconds apart********(look below) about a minute after I bought them, if I get an elite, I put that in the wh and I take the rest of the mets and ref's/uni's, and then two metscrolls, then I go to TC.
Once I'm there, I start upping them. I do one met per item, then do the whole process again. All 3 times, I made the socket at exactly XX:30. This is for first sockets. ***NOTE***: I ALWAYS start with the mets I get from the MB's first to up. And usually after about the 3rd or 4th lvl with the item, I get a socket.
I got a socket in a Unique Necklace LVL 52, Socket in a Ref Ring LVL 30, and socket in a Refined Boots LVL 40. I know this isn't a trick, but some of you might want to try it anyways. Good luck!
********* PS: My theory on MB's is that they are timed. EG: If you open the first MB and its a met and a ref, then if you open like 5 others all really quickly right after, they are all going to be met and a ref. I don't know if this has been mentioned, so basically when I'm actually looking to get decent stuff out of MB's, I try to delay opening each one. I open one, and if it's a ref or uni with a met, I wait like 5 minutes. I have gotten over 30 elites from MB's and only twice I think were from opening a lot all at the same time. Probably a lot of you already know this, but that's just my recent discovery :P