I start from the base of the tree going up. Twisting very tightly at the base part and loosely at the tree part.
Next, I screw the tree into the base.
Then, I glue the presents around the base of the tree.
Next, I add the ornaments to the tree. (I usually follow a pattern of colors)
If the holes in ornaments are a little bit to big for the wire I just hot glue each one down on either side of the hole so it won't move.
Then I take clay (that I cut into the shape of a star and baked) and put it at the top of the tree (sometimes twisting the wire will hold it into place other times glue will)
At the end, if the tree is a bit too wobbly or is leaning to much on one side, I tend to tie it to the presents at the bottom to stabilize it more.