Mac OS X has the very convenient open command to open any file from the command line in the same way that the Finder would.
thilo$ open a.pdf
Is there a similar command for opening the file with Quick Look?
To open files with Quick Look from the command line, you can use the qlmanage command
(Quick Look Server debug and management tool):
qlmanage -p path/to/file
For more information, you can read the manual:
man qlmanage