"It's been real!"

And off he goes.

Cam returns to the house the next day after school.

There's a note resting atop the closed book.

Go ahead.

...oh, well, that was easier than he thought it might be. "Thanks," he says, and he sits down at the desk to have at.

Chapter 3, Actions, is another relatively dry glossary chapter.  This time of the things one does to complete a spell, naturally, instead of the ingredients one uses.  The same capitalization scheme applies.  Also:  hands are really important for spellcasting!  Take care of yours.  You can probably write your own spells which don't specifically need hands if you have to, but actions need to be performed as described.  Here are the page numbers of spells for if you expect to have trouble with that (increasing manual dexterity, hand-specific healing, etc).

Most of the actions themselves are pretty straightforward.  They flip back and forth between entries that are completely mundane and ones that are clearly terms of art that the author defines rigorously.  Many of the latter are in French; the author might be dipping into ballet terminology at times.  

A handful of the mundane definitions have odd specifications to them; apparently using lighters to set fires directly is unacceptable.  Matches work, and so do more primitive methods.  If really all you have is a lighter, you can light some other source, preferably bigger than the one you're going to be using for the spell, enjoy it on its own merits for a while, say the spell on this page number, and transfer it over.

There are instructions on what to do if things go wrong in various ways.  If the wick in a time-sensitive spell won't light, just keep trying; timings are often somewhat lenient if you're already taking the relevant actions.  (If it's not time-sensitive, just keep trying anyways, obviously.)  But really you should be testing copies of your materials beforehand and leaving yourself as much time as you can.  If you mess up a bit of hand choreography, you can make this sharp gesture and start over from the beginning of the move.  If you spill a capitalized particulate ingredient on a table, you can scoop it up again if the table is clean; if you spill it on the ground, replace it or give up on the spell entirely (unless the ingredient is Dirt).

There are not descriptions of what exactly goes wrong if you fail to follow the instructions.

"Would that I had ever been a Boy Scout," Cam remarks, on the page about the fires. Is it safe to practice individual hand motions in isolation?

The book doesn't explicitly say so but some of them are so basic (making a chopping motion, placing a hand on your chest) that at least those ones must be.

Cam dug a plastic spinner out of a copy of the Game of Life that he found in his dad's garage. Charlie says he couldn't give it to Goodwill because it's got a huge rip in the board. So the spinner won't be missed at all. It goes from 1-10, but the spinner can rest on the left or right of the tickmarks that bound each number, or float between them, which is potentially a lot of granularity. "First of all, can you turn this. If you're watching at all, which I guess I don't know."

Sp—spinnnnn.

1 left: yes
1 center: maybe/it's complicated/rephrase that question
1 right: no
2 left: spelling to follow

Left of 1.

Thumbs up. "Is it safe to practice all the gestures by themselves?"

The spinner budges slightly to the right.  Not all the way onto the numeral.

"...do you know whether it's safe or not?"

The spinner floats back and forth a few times, with the needle in the right half of the 1 cell.

"Did you ever try it?"

Left 1.

After some fairly tedious back-and-forth during which Cam keeps accidentally asking negatively framed questions and needing to backtrack to double check whether yes means yes or not, Cam determines that it's almost certainly safe, and starts practicing hand gestures as he pages through the book.

Jeremy turns out to want a separate position shortcut for 'I don't know', over the course of that.

The house isn't the warmest, or the most insulated, so it's hard to tell whether the fact that Cam's left hand is growing colder than his right is due to a natural draft or something spooky.

Well, maybe sticking it in his opposite armpit will help either way.

Tap  tap.

"Spelling to follow or do you want me to guess?"

H A  N  D    W  R  ON G

"I figured maybe you got too close to it or something. Do you think I did a gesture incorrectly?"