Nothing special,just say who made this and finished job!

Pretty much what BokkaB said, yeah. Giving credit just means saying who made something, maybe linking to their save if you know how to, as opposed to taking credit, which means stealing what they did and acting like you made it.

Whenever you copy someone's save or a part of save, you need to mention which save you copied that part from. This can be done either by giving links to the save or by providing save id in save description.

You don't need to give credit (although you should) if save mentions "free to copy"

You can't copy a save if user puts a "no copy sign".

Also it's worth noting that just saying "credit to owner" isn't enough. You need to provide the actual save id.

Or if you modify someone's save for accurate adjustments you still give credit to the original author. An example of that is my U.S. Civil War Map, I fixed errors in the map and gave credit to @Avi_ I fixed U.S. state borders and state shapes. Mainly due to my OCD and I felt like posting a U.S. Civil War Map for history nerds here, plus my state looked like a sore deformed hand. So my OCD kicked in, but nevertheless I still had to give credit.