What if they pay no attention to each other they just swim back and forth but not with each other.
When the female starts digging near a rock and starts cleaning it she's getting ready.
I bred these before I had my female first for about year before I found a nice male. When I first put them together she immediately bonded and she laid down eggs within the first week together. Not saying its that easy but if they don't fight then very good chance when she ready there will be eggs.
http://www.youtube.com/user/vqfive?feature=mhee#p/u/68/VpH6Ag_2_BY
What are u trying to pair up? space and low stress are good factors. they might take longer if the tank is overcrowded.