Marking the Blade
1. If not already done, mark out the centre line on the whole face of the paddle (from grip to shaft). Even though you will be shaving off these lines, they are necessary for other paddle dimensions.
2. Measure the blade (from paddle tip to where it meets the shaft) and divide into thirds. Mark a line across the blade and down the edges 2/3rds up from the tip (ie, 30 inch blade would be marked at 20 inches from the tip). The markings on the edges are the real important guidelines...at these points the blade tapers up to form shoulders with the shaft.
3. Place the paddle on its edge (in a vise) and locate the centre by drawing a short line (maybe 2 inches). For a 1 1/8th thick piece of stock, the centre would be a 9/16ths. You don't need to extend this line all the way around.
4. Take the combination sqaure and measure out 1/16th beyond the small centre line and extend this all the way around the entire paddle blade edge on both sides of the centre line. At this point you have about 1/8th edge guide that I like to shade in with a pencil
5. Adjust the combination square again to another 1/8th beyond the edge guide on either side and mark all the way around the blade up to the vertical marks on the side of the paddle that you marked 2/3rds of the way up the blade in step 2. These outer lines will be for guiding down roughly with a plane whereas space between these lines and the shaded edge guide will be more precisely shaved down with a spokeshave.
Marking the Shaft
Marking out the shaft can involve some complex formulaic methods with a compass and other techniques. To get a round shaft from a square piece of stock can be as simple or as complex as you want. I learned a simple method whereby a stock thickness of 1 1/8th can be rounded using a combination square set at 3/4 inch. Lines are drawn on either edge of the shaft on all four faces for a total of 8 lines. These will be roughly shaped down to an octagon and then sanded to a round shaft
Marking the Shoulders
With the blade and shaft dressed, you can now connect the two at the shoulders. The lines from the shaft have to taper the the thickness of the shaded in edge guide from step 4 with additional rough planing lines added about 1/8th of an inch on either side. The picture below shows this tapering effect. Effectively, the shaded section is what will remain after the blade has been properly carved.
Marking the Grip
Given that grips are highly personalized, I won't go into details about marking out any specific grip. Warren's book has some great ideas for grip patterns, but frankly, this is where the most customization takes place. I'll have some pics later of some of the grip patters that I've worked on but they really are meant for my style of solo paddling with my broad, pudgy hands.