1.
Linux
On Linux, you can use one of these command lines:
love /home/path/to/gamedir/
love /home/path/to/packagedgame.love
If you installed LÖVE system-wide, you can double click on .love files in your file manager as well.
Mac OS X
On Mac OS X, a folder or .love file can be dropped onto the love application bundle. On the Mac Terminal (command line), you can use love like this (assuming it's installed to the Applications directory):
open -n -a love "~/path/to/mygame"
However, the above method will not output printed text to the terminal window. To do that, you will need to execute the love binary inside the application bundle directly:
/Applications/love.app/Contents/MacOS/love ~/path/to/mygame
You can set up an alias in your Terminal session to call the binary when you use love by adding an alias to your ~/.bash_profile.
Open the file with
open -a TextEdit ~/.bash_profile
You may have to run
touch ~/.bash_profile
first if the file does not yet exist.
Then paste in the following code and save the file:
# alias to love alias love="/Applications/love.app/Contents/MacOS/love"
http://love2d.org/wiki/Getting_Started