Use Loci's speed-dating method outlined here:
http://www.bay12forums.com/smf/index.php?topic=144945.msg6028634#msg6028634It works! My fort is 10 years old and I employed this method to arrange pre-honeymoon suites for likely dwarves. Here's my screenshot as I found Loci's a bit confusing:
In the above I have 2 beds - these are
overlapping bedrooms. Create the bedrooms first, and then add the statues after defining the bedrooms. This improves room quality and forces the potential mates to idle next to each other.
Then simply follow these instructions:
1) Remove all meeting areas including flagging the great hall as not a meeting room. This means that your dwarves will idle in their bedrooms
2) Select potential mates. All dwarves need to be
-- Of opposite sex and not gay or asexual (bisexual is fine)
-- Within 10 years of age of each other
-- Not related to each other
3) For the potential mates, remove their existing bedrooms and assign them one of the overlapping pre-honeymoon suites - next to the dwarf you want them to marry
4) Remove all labours from the potential mates, including hauling duties.
After doing this, the potential mates should idle in their bedrooms next to each other, chatting away, making lewd suggestions and eventually becoming lovers and then marry. Whilst it's not perfect and your mileage may vary, my dwarves take about 3-6 months to go from not knowing each other to becoming husband and wife.
Edit:
It seems that each dwarf has a maximum number of possible relationships. Therefore you can get a situation where they're compatible, but because all relationship "slots" are already filled they won't even become passing acquaintances of each other in this set-up. I'm assuming this only happens with relatively large mature forts but the simple solution is to swap the dwarves out with ones that they know already.