A word of caution about this. Servitors are a rather dark and dangerous sort of magick, so if you're just starting out it would be something to avoid for awhile.
But with that being said, there's a book called Creating Magickal Entities by David Michael Cunningham that looks rather promising. Can't say I've read it myself, but I've heard others speak of it. You might try there.
Well, you can make a sigil out of the servitor's name, and you can attach different sigils to that sigil, and invoke/activate it. For example, your servitor "Ted"... you want "Ted" to clean your room. You'd make the sigil for a clean room, attach it to Ted's, and it helps give the servitor direction. You can also place sigils about, as portals, for ease of sending Ted to other places, wherever you need him.
I seem to be pushing the sigils lol, but I love them! XD