It's easy to make a good doweling jig and once you try one of these you'll probably throw out your fancy ones. You can make a simple but accurate and fast to use doweling jig from hard wood such as maple, if you have a drill press.
I don't know what kind or shape of parts you want to dowel together, but for doing typical doweling projects such as making face frame or door panel frame joints, you can simply plane a piece of maple to the same thickness as the framing material you want to join, then rip a strip down to about 2 inches wide and 3 inches long. (These dimensions are just starting suggestions and anything that fits the materials your working with can be used.) Next draw a center line perpendicularly ( is that a word?) across one edge and one face. These lines will meet where the edge meets the face. (this a very easy and simple process but takes a lot of words to describe).
Next clamp this piece of maple in your drill press vice with the marked narrow edge up. Use a center punch to mark the center of the center line on the edge of the maple block. drill a hole the size of the dowels you want to use. if you are drilling a larger hole, you may want to drill a pilot hole first to help prevent the drill bit from "walking" off center.
Now you will need to add the clamping and alignment tab to your jig. Simply screw another piece of the maple, about 2" by 5" to the face of the drilled block which is opposite the one marked with the center line so that the tab extends down 3 inches past the edge marked with the center line and is flush with the other edge.
This completes the jig and if you were able to get the hole drilled on the exact center line you will have a very accurate, convenient, and fast jig when used with a vice grip type clamp or "Creg Jig" clamp. The marked center line must correspond to the exact hole center for your parts to be aligned correctly when doweled. If it does not, you can erase the line and draw a new line in the correct location.
This verbal description may be too difficult to follow so I will try to figure out how to get some drawings or photos added to this post.
Art Schmitt