There is no schematic rule which fits all. Do something which fulfills the license terms and fits the way you distribute your project.
E.g. the MIT license requires
The above copyright notice and this permission notice shall be
included in all copies or substantial portions of the Software.
The GPL suggests
If the program does terminal interaction, make it output a short
notice like this when it starts in an interactive mode:
<program> Copyright (C) <year> <name of author>
This program comes with ABSOLUTELY NO WARRANTY; for details type `show w'.
This is free software, and you are welcome to redistribute it
under certain conditions; type `show c' for details.
The hypothetical commands
show w and
show c should show the
appropriate parts of the General Public License. Of course, your
program's commands might be different; for a GUI interface, you would
use an “about box”.
So yes, you can even have one LICENSE file. You can have folders with one each. You can rename them to like original_project_LICENSE... whatever. Just be clear in what you do and what refers to what modules or parts