Firstly you need a good sucker banana tree that is verified disease free.
Once it grows into a tree (palm) it will eventually bear fruit.
But its the suckers underneath that produce the new trees.
After the tree has bared fruit you need to cut it down and only keep the sucker trees at the base of the parent tree that have broad leaves.
Remove all thin leaved suckers as these are less productive.
Also if you are on a hill keep the suckers at the top of the hill when possible.
Fertilize and the beginning and end of every season!
I hope this helps solve your question.
From Marty Ware: Australian Agricultural Horticulturist!