You can refer to the current working directory with $cwd.  So if you want to call printsth with a path relative to the current working directory, start the line with $cwd.
For example, if you want to call the printsth in the current directory, say:
$cwd/printsth
If you want to call the printsth one directory above:
$cwd/../printsth
Be sure it's a csh script though (ie. the first line is #!/bin/csh).  If it's an sh or bash script, you need to use $PWD (for 'present working directory'), not $cwd.
EDIT:
If you want a directory relative to the script's directory, not the current working directory, then you can do this:
setenv SCRIPTDIR `dirname $0`
$SCRIPTDIR/printsth
That will set $SCRIPTDIR to the same directory as the original script.  You can then build paths relative to that.