For *nix users, here's a command you can use to clear out the contents of a file without having to delete the file and create it new again (which can be especially big hassle if you have to change file permmissions)

cat /dev/null > THE_NAME_OF_YOUR_FILE

Nothing earth shattering. But I find this useful for dealing with some types of log files. When they get too a certain size and I want to delete them and start again I can use this command to delete the contents without having to create the file again.