There is a "sweet spot" where your nocking point will shoot level. If you are above that, it will shoot nock high. If you are below that, it will shoot nock low up to a point, and then start rebounding off the shelf and look nock high.
It's very important to get the nocking point right before anything else. Trying to bare-shaft with the nocking point off is useless. You may find a shaft that shoots reasonably straight, but if the nocking point is off, accuracy will suffer and broadhead arrows will do funny things.
To set the nocking point, I shoot a soft target at 5 yards with no fletching. After the nocking point is found, you can adjust spine until the shafts are close to straight in the target, then you can move back for fine tuning. I adjust until the shafts fly level, then go up just a fudge. It helps with fletching clearance.
Some recurve bows that are designed to be shot from an elevated rest have a nocking point that looks very high when shooting off the shelf. These bows will kick nock high because of rebounding off the shelf at positions that look good, but aren't because of the tillering for elevated shelf.