Flame reading is an easy way to communicate with deities or practice divination. Hell, sometimes i use it just to get a little insight on how my spell is going. Here are the basics.
A high, steady flame means yes
A low, steady flame means no
A short, weak flame also means no
A dancing flame can mean your spell needs more focus or serve as a sign you need to ground yourself and ask again. Sometimes in the case of deities, it can indicate excitement
A particularly violent, flickering flame signals a strong no, sometimes even a warning
A crackling flame suggests the answer to your question is more than just a yes or no
Flame leaning to the left means yes
Flame leaning to the right means no
If the candle refuses to light or goes out before it gives an answer, then now isnt a good time
On the contrary, if the candle will not go out then you're not done yet, especially if its deity-related