Church "Traditions"

A friend asked me about infant baptism last night.  I'm of the opinion that baptism is something a person should choose for themselves, but if it was done to you as an infant, no harm there.  I don't think it precludes you from choosing to get baptised later.  Anyway, it got me thinking about church traditions.

Our church has a communion tradition, where you take the bread and dip it in the juice, and take both elements at once. That's the way this church has always done communion.  The reason why we do it that way goes back two buildings and several years ago.  The elementary school we were meeting in at the time didn't let the church take communion.  At all.  They didn't want grape juice going everywhere.  So the leaders came up with a compromise.  What if we stood the servers on mats, and had people dip the bread in the juice and eat it while standing on the mat?  The school agreed, and a tradition began.

The next building we moved to wasn't that fussed about mess, but we were used to doing it that way, and it continued.  The building after that, our current meeting place, isn't too fussed either.  But we have a tradition now, that's just the way we do communion.

I'm just wondering what other bits of church tradition are the fossilised remains of a "we had to do it this way."  You can get away with saying this is how we had to do it two buildings ago, and there are even good reasons for continuing like this, but at what point do people start digging up Bible verses to support dipping the bread in the juice?  Where does tradition turn into doctrine?