Other people also post themselves open to find new targets, to keep themselves pinned without having to do any work, or simply to stay clear of any gold in an osw. There are many reasons, and most people have their own take on things when they do it.
I believe that is all it takes, the other forumers may have other tips. I have never been open for steals, only attacks.
Being open for steals can be done by hansels, attack builds and oaf's alike. Just make sure your troops are above 20%.
what is there to go into? you get 1/50th of 1/50th of their stats added to your own. the number is static. it stays the same no matter what % of troops you have. what else do you need to know?
more like adds stats per troop. it is the same concept as the bonus you get from the feather sword or other static stat eb items.