Hi. I'm also new to calligraphy. Here's what I picked up from
https://calligraphypen.wordpress.com/2009/01/16/stroking-the-rules/This is the guide that will show us how long the ascenders and descenders will be (e.g. l, p), and the height of the letters (x-height) without ascenders or descenders (e.g. a, o, m).
Since calligraphy doesn’t usually have extra spaces between writing lines, the bottom of the descender line will be the top of the next ascender line.
Tip: One of the most common mistakes I’ve seen by beginners is starting to letter in the ascender or descender space instead of the x-height space. To help avoid this mistake, lightly pencil an “x” at the edge of the x-height space as a visual reminder!
The angle/slant depends on which font you are using. It's 55 degrees for copperplate and 52 degrees for spencerian.
Hope this helps.