Useful links:
Howto count files in a directory (wc will count the lines)
find . | wc -l
if you want only files, use:
find . -not -type d | wc -l
and if you don't want to dive into subdirectories:
find . -not -type d -maxdepth 1 | wc -l
Delete all files not modified 180 days before:
find . -mtime +180 -exec /bin/rm {} \;
Print all files modified within the last 60 minutes:
find . -mmin -60 -print
Print which directories in the current directory occupy how much space (in megabytes):
find . -maxdepth 1 -type d -exec du -ms {} \; | sort -nr