in the spirit of my sig to posts (not wanting to enable aquarists... but helping folks to help themselves)... I have to redirect you at this point, my friend
The link Amy graciously provided above takes you to an article with a literal illustration detailing the very thing you've asked...
... and many posts and pics in the links above (the very purpose for this stickied thread) will do the same.
You will learn much by being adventurous and self-serving. DO help yourself here, mate.