The most primitive of all polespears is the all-wood thrusting hand spear. With no sling to propel it and no metal bards to hold the fish, these are the most challenging spears to hunt with.
You do not have to have a perfectly straight and smooth piece of wood. Since you won't be using a sling, the imperfections of the shaft will not catch on your gloves or spoil your aim. In fact, knots in the wood can be starting points for barbs, and a slight curve to the shaft can help in certain situations.
You can use dead or live wood, with my preference being live wood. Mostly because its easier to find a spear of the right size. A branch or sappling about 3/4" diameter is ideal. Length is a matter of personal choice. I like spears around 3-4 feet long, but I can certainly see the argument for making one a lot longer.
Trim the bark from the front of the spear. You may want to leave some bark on the butt end for a hand grip. Sharpen the point so that the pithy center of the wood is not the middle of the point. A three-angle point works well here and creates a "hollow ground" look.
I have never had much luck adding barbs to a wooden hand spear. I've tried using a knot on the wood as a starting point and tried lashing a strip of wood to a cut-out depression in the shaft. Neither has worked for anything but peace of mind. I think there must be a decent way to make an all wooden barb that works, I just haven't found out for myself.
Perhaps the most important part of the process is hardening the point. Start a fire (a lighter will do if that's what you have), and heat the tip of the spear. The very end of the tip will heat up quicker than the base of the point, so don't put much (or any) heat here. Its easy to burn the point off, too. Try and get a uniform light-brown color on the tip.
If you are used to using a sling powered polespear, one of the first things that will shock you is the lack of power your hand spear has. Its hard to believe that the wimpy little sling band has more power than the full weight of your thrust until you experience it first hand. Not only is the spear so much slower, but the fish will feel the pressure wave your arm creates as you thrust. Naturally, one of the biggest challenges with a sling-less hand spear is that fish will have much more time to react to your thrust.
If you are aware of this limitation, you can use it to your advantage. For example, I have found that a fish looking at you head-on is a perfect target. By the time the spear lands the fish will have turned to flee and the spear will hit it directly in the side. Most of the time this winds up in a gut shot, which is not really a bad place to hit a fish with such a low powered weapon. Although I have not had the chance to try it, its probable that leading a fish in the direction its facing will also work.
As I stated previously, I've never gotten barbs to work that well. The easy workaround for this is to make sure you either grab the fish and hold him on the spear or keep water pressure against the fish to keep him from flopping off. I do this by moving my spear tip down and then towards the surface and/or swimming quickly with the spear extended out in front of me.
As a last word on technique, spearing down at fish and hitting rocks will ruin your tip in no time. In time you will learn to avoid doing this.
-Mario