There are the terms for the license, and some statement that your project is licensed under those terms. The GPL has an appendix "How to Apply These Terms to Your New Programs" that explains how to attach license notices. It suggests but in no way requires that you add the following header to each source file:
one line to give the program's name and an idea of what it does.
Copyright (C) yyyy name of author
This program is free software; you can redistribute it and/or
modify it under the terms of the GNU General Public License
as published by the Free Software Foundation; either version 2
of the License, or (at your option) any later version.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program; if not, write to the Free Software
Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
(remember to fill in the description, year, and author, and to remove the "or (at your option) any later version" part.)
I would also place similar text into a top-level LICENSE file and put the full terms of the GPL into a COPYING or LICENSE.GPLv2 file. The specifics don't matter as long as it is clear that the copyright holder has issued this license.