Re: cedar siding
Putting up corner boards is easy. It's important is to make sure both boards of the corner board are equal, or nearly so. For one-story house , 1-by-5 (4 1/2 inches wide) and a 1-by-4 (3 1/2 inches wide) will work well. Nail the two together so that the 1-by-4 butts against the 1-by-5; this will make the width in both directions almost equal. It's best to nail the two pieces into an "L" shape, then nail it against the corners. For a 2-story house, the pieces can be 1-by-6 and 1-by-5, You need a wider corner board to look right on two stories.
As far as your windows go, I would have framed them first, so a lead drip edge could have been installed under the siding and across the top of the windows.I hope you can still accomplish this. It is important to prevent water from running down behind the window frame.
Tongue and grove siding can be installed like T&G flooring . That is install the siding with the tongue up. Toenail the siding through the tongue and then slide the grove of the next piece down over the tongue. The only face nailing would be on the bottom row.
Hope that helps
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