If I use code from a GPL'd project, where should I put its copyright notice? Would just putting it in a README be fine?

You can only incorporate code from a GPL project if you project itself is GPL. Therefore you need to add the GPL notice as the header to ALL of your source files, in addition to providing a copy of the license with your source and your executable.

Note that LGPL is different from GPL, and LGPL code can be linked to (in DLL form or similar) without forcing your code to become LGPL.

You can only incorporate code from a GPL project if you project itself is GPL. Therefore you need to add the GPL notice as the header to ALL of your source files, in addition to providing a copy of the license with your source and your executable.

I understand that but, do I have to put the name of the project it's from and if so where do I put it.