The proper sign for this word depends on your meaning or intent.
If you want to talk about a wrist watch, you can sign:
The sign BRACELET could also mean "watch"
If you want to talk about "watch" as in "look at" you should check out the "SEE" page for a more complete discussion of this topic. But I'll include the main "watch/look" variations here:
WATCH: (to look at something)
look at that:
WATCH (be looking at/more detached/spectator)
watch: (regional variation)
