Good recommendation. Tone is a hard concept to grasp in writing, even experienced writers struggle with this. (This is why editors exist as well.)
To help with this, I would try practicing different tones on the same action.
We can use "walking into a cave" as an example
For a more serious story with lots of action, stick with serious to the point tone.
"He went into the cave, a stern look set on his face as he drew closer to the cavernous mouth."
For a more informative tone, use more formal language and give qualitative and quantitative descriptions.
" He noticed a increase in humidity, as he took a few steps into the cave, and noted it in the back of his mind."
For a more laid back and fun tone, try writing something you would see in a casual adventure story.
"He bounded towards the cave with a gleeful expression plastered on his face, and he laughed as his team sighed at his antics."
There are several more, but hopefully you can get how the same scene can have different tones depending on the use of vocabulary.
Another point to think about is the shift in tone. For instance, you can use a shift from a serious tone to a non serious tone to create humorous scenes. (Look up gintama for the best examples of this)
Another shift in tone is from a casual tone to a serious tone. Look up made in abyss for a good example. It uses the shift from a lighthearted adventure tone to a dark deadly journey towards the bottom of the abyss tone as a way to shock the audience and keep them interested.
There are some pretty interesting relationships between tones, so it might be worth it to research a bit into it.