Depending on the wood and what you are looking for, the angle will vary - 30-45 is common. If you can get some pieces from the corners, turn them round with different angles to the grain and see which angle give you the best effect you are looking for. I tend to like the 20-35 long elipse grain shapes.
Color addition can make a big difference in appearance depending on the wood. Some like Zebra and marble wood look entirely differently cut 90 degrees cross grain - but tricky turning.