how do i determine what length arrows i should be shooting?

ben pearson quad 440
69# 28"

Depends on the spine of the shaft and the overall (point + insert)tip weight. To a lesser degree, the fletching and nock. You should also have a good idea of the FOC (12% is a good start) you are trying to achieve.

draw your arrow back fully/have someone mark it at where it is on the rest/add 2 inches

Everyone may want their arrows to be cut different. I shoot a 28" draw and have cut my arrows 27.5" for years. When I build an arrow I choose spine, etc, based on that finished length.

While you can add length, it is not necessary unless it makes you feel more comfy.

Things to remember when building a set of arrows are:
1. make sure all parts, inserts, nocks, etc, are installed properly and are straight
2. Proper spine
3. Proper FOC
4. The best fletching that works for you. Don't be afraid to experiment during off season. I do every year.

Dan

The starting point is 2" longer than the distance where your arrow contacts the rest. However, you can go as low as .5" with some rests to achieve proper spine. Don't use your DL as the starting point. Depending on your rest you can cut some arrows 3" or 4" shorter than your DL.

Unless all the manufacturers you are using provide the exact same spine you often times have to change the arrow length to get a proper spine.

I get mine cut about 2" past my rest and pick a spine according to that. It turns out for my Alphamax that my arrow length is exactly my draw length, I think you will find this to be pretty close on most bows.