I started with satellite arc info, then printed off my yard in google maps, that was the most up to date. From there I drew in the limits of the arc I wanted to see.
For locating my dish, I put it so the tallest tree was due south at about 87w or so. And I could still get Alaska (at least when the beam was in my area). Plenty of room for the trees to grow over time, because they will. The dish ended up being about 120 feet from the house so I had to size my wiring accordingly but it’s been worth it.
I used a cheap little map compass, with a rectangular plastic frame. Taped to a yardstick. Compensating for magnetic adjustment. Sighting down the stick, I could pick a feature in the distance to line up with based on where I was standing.
For elevation, I used a plastic locking protractor set at the target elevation. With a digital level on the horizontal. These days I could just use a free phone app, zero it at the angle I want, and have it beep. Hold it against the yardstick and sight down it to see if everything will clear.
For actual dish alignment I first held the yardstick against the mount, with the compass at the far end so the steel didn’t interfere. For elevation I just held the angle finder against the mount. I actually was in the zone for 87w from the first try, bumping the dish brought in channels I already had scanned from the old house.