My favourite way to candyflip has always been.
00:00 - Dose LSD
04:00 - Dose MDMA
05:30 - Redose MDMA
With marijuana, N2O and benzos on hand.
edit: Make sure the pills are clean, you might want to test them. Dropping a meth-bomb or pill full of piperazines with a head full of acid wouldn't be nice at all!!
Though I have had fun with some psychs and meth/speed before but only because I knew what I was taking and could dose it all accordingly, have had shocking experiences on the same combo too (acid and speed), so it's not a sure thing anyway for a good time. Make sure it's MDMA, or atleast an MDxx substance.
Hope any of that helps.
2nd edit: Also as DarkSideoftheWall said, don't over-do the acid as it will take over and you might not even notice the MDMA because you're tripping so hard. I'd recommend a low-medium dose of the acid (0.5 - 2 hits depending on how strong the paper/liquid is) and to take 3/4 of your usual dose of MDMA (just in case, candyflipping can be intense) - otherwise I'd go with your usual dose of MDMA, though others may disagree with me.