If you get green wood off a tree, make sure to dry it first. de-bark it, and apply a sealant (varnish, wax, etc.) to the ends.
Step 1: Materials and tools.
(murphy carver: http://www.leevalley.com/wood/page.aspx?c=1&p=53890&cat=1,130,43332,43339)
(flexcut detail knife: http://www.leevalley.com/wood/page.aspx?c=1&p=31090&cat=1,130,43332,43393)
strop with stropping compound (sort of optional, if you don't mind having dull knives...)
Gloves(also optional... helps with gripping the stick and protects your hands
Leather lap apron(optional. it helps protect your knees and legs if you are carving while sitting with the stick in your lap. i have a few pairs of pants with holes in them from before i got one of these...http://www.leevalley.com/wood/page.aspx?c=1&p=55073&cat=1,130,43332)
Chisels(optional. they help quite a bit when you're carving things... you can do a lot of things that are hard to do or impossible with a knife with chisels.)
Step 2: Get a stick.
check to make sure there is no rotten patches on the wood you are about to take. if you are cutting a branch from a tree, make sure you know which branch you want so that you don't have to cut off another one. If you see a bird's nest avoid the branch it's on, and try not to disturb it. If you see a branch that you would like to get in the future put a marker of some sort on it (brightly coloured tape, a piece of rope, string, etc.) and return later.
Also, make sure the wood you get is sturdy enough to be used as a cane or staff.