Minecraft wiki entry for Tree_farming, associated text: Top down: get up and cut down. Less thinking needed and more efficient for fast (enchanted diamond or netherite) axes.
Getting up:
For jungle giants, you can use those shears to harvest vines from two or three sides of the trunk to complete a track to the top, breaking or shearing the upper leaves.
For giant spruces or if you can't be bothered with the vines, you can just bring a half-stack of ladders. If you do need ladders, but haven't got them, you can take a block or few of wood in a column (that is, a groove up the trunk), use those to make some ladders, and run the ladders up the groove, making more ladders as needed and as you mine the tree. You might need to make a crafting table with the first block.
When you reach the top, find one block of wood standing above the other three. Chop that to start the canopy decaying.
For jungle giants, it's best to stand on the trunk and clear all foliage above your foot level, then use the remaining leaves as a floor to get at branches and the edges of foliage. Go down level by level like this until you've got all the branches—watch for knots of foliage that aren't decaying even though they're separated from the trunk.
For spruce trees, it usually suffices to cut away the foliage from the trunk (as far below your level as you can reach), to speed decay.
When you've got all the branches for a jungle giant, or immediately for a giant spruce, you can simply cut your way down the trunk.
Spiral up: cut a staircase out of the tree. No extra tools needed. As fast as top-down for normal axes.
Start by cutting three bottom blocks (height 1,2,3) out of the right (or left) side the tree. Go inside the space you just created, cut up three higher blocks (height 2,3,4) on the neighboring part. Go up that block, turn left (or right), and repeat (height 3,4,5) until you make it to the top.
Now make you way down by going down four stairs, chopping away what is above you, and repeat. If you have see a branch, cut that down first, using the leaves as a floor.
When you are on the ground, just finish up the little stump you have left.