How to tell balsam fir from spruce

The flat, soft needles of a balsam fir

Spruce needles are like a stiff bottle brush

I often hear Boreal newcomers mistake balsams and spruces. Their basic shape is similar so it's an easy mistake to make.
If you can grasp a branch, you can quickly tell the difference. Balsam firs have soft needles. You have probably had a balsam for a Christmas tree at some point as they are commonly farmed for this purpose. You can hang ornaments on their branches and not prick your hand. Not so with spruces. Their needles are like stiff bottle brushes.
The balsam needles are not only soft but are flat in shape and are arranged on either side of the branch. Spruce needles are four-sided and go all the way around the branch.
Balsam are very aromatic. Spruce have little smell.
There are lots of other differences but this is a good place to start. Just run your hand along the branch.