Step 1: Supplies
Paracord can be found at local Army/Navy stores or from various online sources: Supply Captain, Lighthound, Cool Glow Stuff!, ebay, etc...
The actual amount of paracord that will be used depends on your wrist size. My wrist is about 8.5 inches and I actually used around 8 or 9 feet after finishing the bracelet/watchband. So using 10 feet is a safe estimate for most folks, since having too much cord is better than coming up short when making your project.
*If making a watchband, the watch needs to have about 5/8" space between the lugs(where the watch pins go) so that 5 strands of paracord will fit.
Step 2: To begin
Step 3: Add the watch and adjust for wrist size
At this point, you'll measure the distance between the buckle ends for your wrist size. The distance should be equal to your actual wrist measurement. The weaving process will stretch this original spacing of bracelet/watchband about another inch after tightening as you reach the finishing point.
*Don't include the prong section half of the male end of the buckle in your measurement. It is snapped into the female half of the buckle when worn and isn't used in figuring the wrist measurement.
Now bring the cord ends back thru the watch pins, along side your first pass, and around the starting buckle end.
*If you're just making a paracord bracelet, you'll just be going from one end of the buckle to the other without adding the watch.
Step 4: Begin weaving
This weaving process is called 'weaving with three warps'. You'll be going around the outer cord with your working strand, under the center two cords(which you treat as one cord), and around the other outer cord.
You weave it back over the center two strands and around the outer, continuing this process, back and forth. Try not to leave too much slack as you go to keep the weave uniform. Every couple of weaves, push your work tight, up towards the starting buckle end.
Step 5: Threading the watch
*If making the bracelet, there' s no watch in the way, so just keep weaving. ;)
Step 6: Continue on the other side of the watch
A pair of hemostats can help work the cord around as you get close to the buckle end, making the last couple of weaves.
Step 7: Finishing up
*Check for a good fit on your wrist at this point. If it's too loose or too tight, untie, adjust your starting measurement longer or shorter to correct, and try again. I have to do this myself sometimes. ;)
Take your hemostats and work them thru about three of the center weaves, towards the buckle end. Grasp the working strand and pull it back thru the center weaves.
Trim the end with your scissors, quick melt the end to prevent the cord from fraying, and tuck it under the weave.
Now do the same with the shorter end of cord and you're done.
If you measure again, you'll see that the finished length is about 1 inch longer than the starting measurement. This will vary depending on your tightening of the weave as you go, but should make for a loose/comfortable fit.
*Anyone that's worn a nylon/paracord bracelet/watchband knows it can get dirty and smell funky after a while of use. I use an old soft bristle toothbrush to scrub with soap/water in the sink to clean it(while it's on the watch(hopefully yours is water resistant/waterproof), and let it air dry overnight.
*A note on paracord shrinkage:
Ubraidit.com mentions that paracord may shrink as much as 10%-12%(especially black and kelly green), so they recommend soaking the cord first. They note that it's the inner strands that shrink, not the outer sheath. I believe they use 450 or 650 grade paracord, which I think, has a few loose fibrous polyester filler cords instead of the usual 7 twisted nylon strands, found in 'Type III 550 mil-spec paracord which isn't supposed to shrink up. I've mostly used the mil-spec type paracord, so if it's shrunk on me, it's not noticeable. YMMV ;)