I had an idea for a sitcom and am writing scripts for it (I'm on the fourth one now.) I use the font Courier 11, and the scripts roughly amount to about 24/25 pages. I'd suggest transcribing an episode of Malcolm in the Middle and typing it up in the normal teleplay format (either Courier, or Courier New is used, and the number is usually 12, although I myself am using 11 on my computer) and see how many pages it comes to. Then that will you give you an idea of how many pages to use for your own script.
I've been on some websites that tell you how to set out a screenplay or a teleplay; unfortunately I don't recall many of their names, but Wikipedia has some information on screenwriting. By "screenwriting", it mainly refers to writing movie scripts, but I think a similar method of writing applies to scripts for TV as well - i.e. I believe the same font is used for both movies and TV shows, and the terminlogy remains similar - for instance, at the beginning of your script, you'd put the scene (usually this is done in letters, so you'd have Scene A, Scene B, Scene C, etc...and there are usually two acts...after you've written "Scene A" or whichever scene it is, you then type the setting and what time of day it is. For instance, let's have a scene with Lois and the boys in the kitchen:
ACT 1
SCENE A
INT. KITCHEN - DAY
LOIS IS PUTTING BREAKFAST
ON THE TABLE. MALCOLM AND
REESE ARE FIGHTING ON THE
FLOOR AND DEWEY IS FLICKING
CEREAL AT THEM.
LOIS
Reese! Malcolm! Stop fighting and eat your
breakfast this instant! Dewey! I can think
of a far more productive way to use cereal
than to throw it at your brothers! Eat it!
You should be thankful you're not one of
those poor little starving children...
Anyway, that's kind of how a screenplay/teleplay would look. I don't think it's entirely 100% accurate, but I think it's pretty close.
EDIT: The part where Lois talks should be in the centre of the page, but it won't remain in the centre on here. But on a screenplay/teleplay format, the speech is in the centre.