Disclaimer
I am not a lawyer, so you should really consult with one to get absolutely correct answers here.
To the best of my knowledge...
Whenever you author something, whether it be code or anything else, you automatically become the copyright owner of that work (unless you've signed an agreement whereby it is "work for hire").
As the copyright owner, you can apply whatever license you like. The fact is that, if you don't give out a license, then no one has any right to use, copy, modify, distribute, etc. your coyrighted work. So, users need your license to have permission to use the project (if you don't give a license, it cannot, contrary to popular belief, be presumed public domain). So, you don't need to worry about people ignoring the license... if they can't point to a license where you grant them rights to use your software, as the copyright owner, you can sue them for using your copyrighted work without your express permission to do so.
It is typical in open source projects to place the license in a file named "LICENSE" or "COPYING" in the top-level directory of the project. I suggest that you stick to this convention, since that is where people will look for the license. It is also good to indicate what the license is on the project's website, so that people don't have to download your whole project before they know what the license agreement is.
It is not necessary to include a full copy of the license in each source code file, although this is fairly common practice. Keep in mind, though, that putting a full copy of the license (or at least some indication of copyright ownership and the name of the license, if it is a well-known license) in any header files that you install will avoid any confusion as to where the header files originated, so it is reasonable to do that.
If you own the project and others contribute in a fashion similar to "work for hire", then it is not necessary to name the contributors. However, you should make it explicit (and get a permanent record of an agreement from contributors) that you will remain the sole copyright owner of the project, despite contributions made. Otherwise, the contributors do have copyright ownership over the files/code that they contributed.
One last thing, not related to the question... I highly recommend that you avoid GPL and LGPL, and go for a more permissive license (e.g. MIT, New BSD, Simplified BSD), as the former will limit the adoptability of your code, and projects with more liberal licenses, if they do become adopted in the industry, have the potential to be backed by the industry (e.g. the Apache Foundation has strong industry support, because, unlike GNU/FSF which mistakenly views open source and closed source as enemies, sees them as collaborators, and so uses licenses that allow their projects to be widely adopted by the industry world).
