Before you cut or do anything, take a look at OL's website:
tuning web page . While he's not the originator of this form of tuning, he did a great job at explaining it and clearly laying out the directions. If you follow the instructions exactly, you will get superb arrow flight. Let me know if you have questions after reading it and I'd be happy to help.
A few key tips: set up the arrows exactly as you would shoot them, put on whatever cresting or wrap you will use if any, same point and insert etc. I use just a drop of superglue or even hot melt to barely hold the insert in so you can cut from the front of the arrow since you have fletching/wraps/cresting you don't want to mess with. You will have say 4 arrows fletched and 2 arrows unfletched (I've found this to be a good number to work with) to do the relational testing like this. Make sure they are all the same, except for the fletching. Change only one thing at a time and do the same for all arrows at the same time; meaning, don't cut the shaft and add/reduce point weight at the same time or do it just for a few of the arrows. Cut carbons in small increments; the difference with in-tune and out can be as little as 1/4" or less.
Again, follow the instructions to the letter, barring any equipment issues, and you WILL get good arrow flight with this method.