oil gallery plug installation

I was wandering first is it oil gallery or oil galley plugs I have seen it both ways and when I search for info on them I get matches from either spelling. Anyway I was wandering what the proper procedure for installing them are? I have seen one site that said to turn them three full turns only. I have seen one that said to turn them until they are flush with the block. I haven't tested to see if these are in turn the same amount but I don't want to strip anything trying to find out so if any of you have a sure fire method please share it with me. Thanks

It's 'gallery'
These are pipe threads, so as you screw them in they will get progressively tighter. This is because pipe threads are designed with a slight 'interference fit' to help sealing. Screw them in until they are reasonably firm. Use a sealer on the threads. You can use teflon tape of silicone but I prefer plumbers threaded joint compound (like a paste) used for threaded iron pipe.