Squaring pergol

Building an attached pergola. What is the correct way to ensure I get the two outter posts square to the house and that the entire pergola is square?

Also -- what's the easiest method to ensure I get the posts at the correct height? I plan on digging the hole to the depth that I need (versus trying to cut the 8x8 post to the exact height).

Thanks

 

For the "squaring", I'd use the old "3-4-5" method. A triangle having sides of 3, 4, and 5 has a 90 degree angle formed by the sides of length 3 and 4. There are many variations on what/how to create the triangle, so please give us more info.
(one example: from the point on the house where you want the pergola to extend, mark a length of 3 feet along the wall.On a string attached to that point on the wall, mark a length of 4 feet. As you rotate the string, use a tape measure to measure the distance between your marks. When that distance (from A to B in the diagram) is 5, you have a right angle.
If you create a right angle at all 4 corners, the pergola will be square to the house.
(The attachment below is a so-so drawing, that I can't seem to get into the post!)


Regarding post height: I'd suggest using a level (laser, string, etc. to measure the height of the posts, rather than trying to dig different depth holes at different points in your yard.IMO, cutting the posts would be easier. Hopefully, some of the pros will be along shortly.
Good luck with your project.