There are quite a few sites with instructions for making freeform bracelets and necklaces.  Basically, you just grab a bunch of different size seed beads, some larger accent beads and just start stitchin'!

You can make freeform pieces using either peyote/ gourd stitch or brick stitch, whichever method you're more comfortable with.

This bracelet was finished in just a couple of days.  It was lots of fun, and it made up quickly because there was no pattern to follow.

Bracelet Foundation:
I started the bracelet using different size seed beads, but it soon began having a very definite curve... the more I stitched, the more like a U it became!  So I started a new bracelet foundation using all Delicas in a semi-patchwork pattern of blues and browns.   made the foundation about 1" wide and then made it just a tad longer than my normal bracelet length. 

I'd read somewhere that because of all the embellishing, you need to add a half-inch or so to the length, but I ended up with a bracelet that had overlapping ends, so that may not be the case if you use all same-size beads on your foundation.  Ultimately I think making the foundation true to size would be your best bet - you can add beads to the ends easier than you can remove them!

Enlarging the Foundation:
Next I started adding small sections of different size beads in various points on the outside edge of the bracelet.  Mostly these sections were rectangular, but one was triangular and one was a netted scallop.  These sections were primarily on the ends of the bracelet to add stability, and I still pretty much stuck to using just the different size seed beads

Embellishing:
Then it was time to have some fun!  I tried to use as many patterns and combinations of beads as I could remember, find in books, or accidentally come up with. 

I made "bridges" to connect the patches to points farther along the bracelet, to other patches and even to other bridges. 

I added fringe- or picot-like combos of beads (such a hex bead with a tiny 14/0 bead at the tip) in place of patches in some cases.  These served to add movement and interest to the bracelet.

Another attractive thing to do is make X's or diagonal lines of strung beads - and even these could be embellished with picots.

Finishing the Embellishment:
The hardest part is making yourself STOP!  Actually on a bracelet, you can drape it over your wrist and get a good idea of when enough is enough, but I've just started a collar, and I can imagine how it could easily end up a halter if I'm not careful!

To finish the embellishing, I added larger freshwater pearls, semiprecious stones and some small lampwork beads in places where it just looked like it needed something.  On the heavier beads, I doubled my thread.  Be sure to run your thread through quite a few rows in opposite directions to give the beads (and the bracelet) stability -  especially on beads that dangle.

Adding a Clasp:
As with many of my beading projects, its the process that I enjoy more than the wearing... so I haven't put a clasp on this one yet!  I'm thinking a snap or something similar because the ends overlaps a bit.  I think a vintage button with a loop closure would be nice look, too.
    

And if you have any questions, please feel free to email me!

You can see better detail on this scan, but it's over-exposed!