First mark out the paddle form, I have included a picture below with measurements, mark off the base of the paddle 3 1/2" from the tip and then another line 1" - 2" from where the handle starts, to make the transition from the handle to the paddle mark off 1/4 of the width and then draw a line from the handle to the line 1"-2" out, then a line from all the way to the end of the paddle using the line you put at 3 1/2" as the intersection point. Shoul be fairly straight forward using the diagram below. To draw the end of the paddle (curve) use a plate and just align the end of the plate and draw a half circle. Do the above on both sides of the paddle. This is where exact measurements from before will come back to haunt you, the lines need to be perfect on both side otherwise your paddle will all be crooked.
Now get out that trusty jigsaw (or bandsaw if you have one) and cut out the paddle blank, I found if using a Jigsaw, don't cut on the line as the blade is far from straight, I left a 1/4" inch space and then planed the difference down. If doing what I did, make sure when planing that you keep an eye on the lines on both sides to make sure you are even, the more time you spend making it smooth the better, mistakes here will come back and haunt you, as I found out with mine.
Now your paddle blank should be complete, for mine, I ran over the entire paddle, all edges and sides with sand paper to make sure everything was smooth. Picture below shows my paddle blank completed and ready for final shapping.