I am in the process of finishing up my deck plans for my summer project and I have been getting mixed results from the lumber yards I have been dealing with of the best way to attach my 2x10 beams to my 6x6 posts. Because of the height of my deck and that it is not going to be covered I don't have any zoning or building codes that I have to follow for my deck so they are not providing any reg's for me.
Basically, I have two concepts for how to attach the beams to the posts.
First, notch the top of the 6x6, thus creating a ledge, to fit a 2x10 on on opposite sides of the 6x6, and screw/bolt/nail the 2 - 2x10's and 6x6 together with the 6x6 sandwiched in the middle. The outside surface of the 2x10 and 6x6 would be in the same plane.
Second, bolt the 2x10's with carriage bolts to the side of the 6x6 without a notch (2x10's would appear to be hanging off the side of the 6x6) and the 6x6 sandwiched inbetween.
Notch one side of the 6 x 6 and attach the two 2 x 10 that have been bolted together. Seal the top of the 2 x 10's with something like Vycor to keep out water. You don't want to bolt without a notch and have to rely on the shear strengh of the hardware to hold it all together.