For years I had trouble with getting my broadhead arrows to shoot well. Dan Quillian introduced me to bare shaft tuning, and it made all the difference. I found out that I had been chronically underspined, so when I put broadheads on they tended to dip and swerve before hitting the target, or somewhere close to it.
I shoot wood exclusively, so I shoot a very soft foam target from close range and go by nock left/right/up/down. I set the up/down to just barely nock high, then change spine until I get a straight in shaft. I don't trim my arrows to adjust- instead I have a full set of bare shafts in multiple spines and two-inch different lengths, 28", 30", and 32", all with 125 grain field points. For my longbows I shoot the 28's until I get the right spine, and I use 30's for recurves, which I tend to draw a little longer. The 32's I rarely use, generally only when a long-draw friend needs help. If I want a shorter arrow than 30", I bare shaft a little weak with the 30's and them make up my actual arrows at 29". If I'm going to use broadheads heavier than 125, which is most of the time, I bare shaft a little stiff with the 125 field points. When I then shoot broadheads, I do the final adjustment by changing broadhead weight if necessary. This technique invariably get me perfect broadhead flight, which is the final objective.
I agree with Bowmania- don't bare shaft with broadheads! Not only can it be dangerous, but you must have absolutely perfect form every time. I don't know anyone who is that good, and it will just lead to frustration.
Bare shafting is also good for tuning your bow. In order for it to work smoothly, the bow must be braced at the correct height with the nocking point in the right place. That's the first order of business to get the best arrow performance.