Lettering for architecture and technical theater is basically the same. Lettering can be very pretty and stylized or it can be fairly boring. What it must be, all the time, is clear and legible. For tech theater paperwork we always use capitol block letters. This can get boring quickly. So, we add some style. A slight slant does wonders. A nice curve to some letters. I've known people who get jobs because of their lettering. Think about it; the person hiring wants to have others think highly of the paperwork coming out of their design studio. If I'm the designer and my assistant is drafting the lighting plot, I want the lettering to have a professional flare.

How do we get our lettering to be good? Practice, practice, practice. I've known young designers who have copied the front page of the newspaper to practice.

Lettering comes in different sizes, or heights. 

What you're labeling Size
Dimensions & Notes 1/8" tall
Set pieces & Page titles 3/16" tall
Show Titles (the most important) 1/4" tall

Here are some guidelines for proper lettering:

bullet Practice!
bullet Use guidelines. Draw two very faint horizontal lines; a top and a bottom and then place your letters between them. The top of the letter touches the top line and the bottom touches the bottom line. It's ok to add style here. For example, the letter T. The bottom of my T's tend to drop down below the bottom line. Almost three times farther down past the line. You'll see in the example.
bullet Practice!
bullet Keep track of you spacing. The letters shouldn't get to tight. However, some letters should be closer then others. For example, the word "AT." Look at the two letters, the A and the T. If you had the same spacing of AT as you had for the word "AN", it wouldn't look right. Check it out: AT AN. Take a close look. Doesn't it look like the A and the T should be closer? You can do this. Simply make the left wing of the T overhang the right side of the A.
bullet Practice!
bullet Check your spelling. If you have to, type it on a computer and do a spell check. Then copy it to the drawing.
bullet Practice!
bullet Remember that the drawing is just that; a drawing. The lettering is simply to clarify stuff on the drawing. Too much lettering can be distracting. A picture is worth a thousand words. Make the picture do the talking.
bullet Practice!
    

I'll be scanning in a few examples soon.