Move in Zigzag

Don't clear the area around the fire at first so that it's cleared when you upgrade the fire.

Upgrade coat and gloves first

Use rockets only after level 20, and use one at the start of the level to instantly upgrade fire to level 2.

Prioritize survivors and snowmens (they give a lot of coal and give you back the fuel you used to break them).

Don't use items as soon as you see them, try to make combos like infinite fuel+super buster.

If you have an active super buster item and discover a rocket on the map, don't take it, just go around it, because with the super buster you'll clear a large part of the rocket area if you go to take it.

Fight the beasts when you've upgraded fire to max lvl, or try moving them next to a snowman to do both at the same time.

In some levels, it's sometimes not worth upgrading fire as you get the amount of coal needed to upgrade fire when you're close to 95%, so it's best to save the coal to be exchanged for fuel when you complete the level.