I don't know the best way but here is the way I do it which is a little different than the others(and pesos are worth less than cents the last I heard). I dig all the holes, add about 6" worth of gravel to the bottom for drainage, and insert the posts. Bell shape the hole to avoid ground heave. I go ahead and install the bracing (string lining everything as Jim suggested) between them before leveling with stakes, etc. as Jay suggested and then pour the concrete (as Wick suggested) to the top with a crown. I use to put the posts in first and set them in concrete, but then I would try to span them at 8' with bracing and it seems like there is always a post that is an inch or two off center and off line and my 8' braces wouldn't fit.
I also used to leave the concrete a few inches below ground level so grass would grow but after having some posts rot off at concrete level I learned to crown the cement above ground so water won't sit at the post/concrete edge.
I leave the post top about 6" or more above the upper brace(s) and you don't need to be all the way even with the top of a 6' fence. I stringline and cut the tops after the concrete has set up and before screwing on the fencing.
With the high wind loads, gumbo clay(that dries in the summer and leaves cracks you can stick your hand into), and ground heave around here, I try to bury 2.5' to 3.5' below ground. This is more than many do, but there are many leaning, crooked fences around here. Go deeper for corner posts. I also find that spanning 6' to 7' instead of 8' between posts helps with the wind loading. Bury your corner and gate posts deeper than the others and use longer posts if you need to.
Order your gate posts 2' longer than the others. Besides burying them deeper, get two 2by8s, or 2by10s, or 2by12s and cut a 2" notch so they sit between the two gate posts with the rest of the notch sitting on top of the posts. Screw them in after cutting a nice curved design in the top for decoration purposes with a jig saw(use your imagination here). This keeps them spread and held together square so you don't have misfitting gates 5 years from now when the wind blows them out of align. Set them at standard door height.
I switched to square drive screws (stainless or dacrotized) after after having problems with nail pops after 10 years in old dried out cedar. My nail gun was fast but it buried the heads which were small and my roofing nailer has too big of heads and the nails were too short.
Think about having one fence section that you can bolt in and out in case you want to drive in some time. Have at least one gate (or more) wide enough to drive a riding mower through with out squeezing through and raising the discharge. This is all I can think of for now. Good luck.