Daily, Weekly, and Monthly Computer Hygiene

I you should use a Macintosh running OS X, then said OS needs to do some maintenance on a regular basis. If the computer runs through the night, it will take care to run the necessary steps itself. BUT if you are a good citizen of this planet, then you told your system to go to sleep when not in use for some time, to conserve energy.
Here is the catch, like you are brushing your teeth every morning and evening (or more often), the computer tries to keep itself clean. You cannot brush your teeth while asleep, do you? Same goes for your Macintosh, if it sleeps, it cannot clean the system.
Apple set up three cleansing rituals for the system, but these rituals tax the system considerably. For that very reason, these rituals (vulgo: cron-jobs) are scheduled to run sometimes during the night. On a side-note: if your systems seems to get unresponsive during the day, check the setting of your timezone; the machine might think that the time is somewhere between midnight and early morning and starts the cleaning (another reason to set the correct timezone).
Back to the problem every environmental conscious being faces, the computer cannot take care of the cleaning, but there is hope (you already guessed it, didn't you?). One can easily start the necessary programs by hand:
sudo sh periodic daily
sudo sh periodic weekly
sudo sh periodic monthly
Can be run in the terminal at the appropriate times. One word of caution, though: the weekly and monthly scripts can take a considerable amount of time to finish, plan accordingly.