Well, I certainly have the inside scoop on how the pros do it (I worked in Christmas retail for several years), and I’m a bit of a tree nazi, so here’s my not-so-secret method to tree-decorating:
Lights (always) first. Bend and twist the branches of a fake tree into some semblance of tree-hood first. You need at least 100-200 mini-lights per foot of tree. I start at the bottom and go around in a complete spiral. Wrap each branch - I start at the inside of each branch, wrap out to the tip, and wrap back to the base of the tree, then go to the closest branch. NO wire should show if you do it right. I learned from the pros, what can I say. My mom just watched something on tv (think it was the White House holiday special) where the decorators started many strands of lights at the bottom of the tree and worked straight up (instead of the 'round in circles method.) I may try this next year. Now that you’re done w/lights, if you have a fake tree, further bend it into tree-hood.
Regular decorations (ornaments and such) go on next. Plan ahead and take a look at what you have and the placement of your tree. If your tree is in an inaccessible corner, you won’t need to put stuff on the back! You’ll need much more stuff for an all-around tree.
Think seriously about adding ribbon, silk flowers, garland, etc. All are a great way to make your tree look amazing. Buy slightly more than you think you will need. You can put these on while or after you are adding ornaments. If you add this stuff after ornaments you may need to re-position some ornaments.
You can apply strings of things (tinsel/garland, bead garland, popcorn strings, long lengths of ribbon) in several different ways. You can attach them to the top of the tree and bring them straight down the sides of the tree. You can start at the top and randomly drape the stuff down. You can spiral around. You can secure droopy stuff with wire or ribbon or w/ornaments on the tree.
Never, ever just throw random clumps of string tinsel at the tree. You will burn in hell! (joking) The small handful or single strand method looks much better.
Be creative in you choices and try to come up with some sort of plan - it will work out better if you have an idea of what you are going for.
That’s all I can think of for now - any questions?