You can tell more from shooting a bare shaft into the target than you can from fletched arrows. The problem is, you need to have reasonably good form to shoot a bare shaft. Otherwise, one will go one way and the next will go another way.
But if you shoot a bare shaft that is right for your bow, it will fly to the target as well as if it was fletched. If it veers to the right (for a RH shooter), then you need a stiffer arrow, and if it veers left, then you need a weaker arrow. If it veers up, your nock is set too low. If it veers down, then your nock might be set too high, or you might be getting bounce off the arrow rest. Raise the nock way up until you are sure it is too high, and then work your way down 1/16" or so at a time until you eliminate all the nock high you can, but don't go any lower than that.
For a more comprehensive approach to doing this, check out
http://bowmaker.net/tuning.htm Sometimes the target material will make the arrows stick in at a different angle than the angle they hit the target, so I wouldn't worry about that too much. Look at arrow flight and see if there are any wobbles, up and down or sideways. If there are, then get into arrow tuning. If the arrows seem to be flying straight and steady, then just enjoy shooting the bow.