I assume that you have fully read up on CS prop operation and are expecting the additional workload: you may already have imagined the circuit procedures in your head. If so, good, and it would be impertinent of me to pre-empt what your instructor will want to say on the differences training itself. You don't say which Arrow you will be flying, nor which fixed-gear PA-28, and there are some significant differences, but I can make a few non-obvious suggestions on the assumption you have previously flown the Warrior and / Archer II/III, and are moving to the taper-wing Arrow III:
- The Arrow III is heavy. It has big tanks, a heavy retracting undercarriage, a heavy CS prop. The wing loading is substantially greater than the Warrior. So if you approach at the same speeds, you are more likely to be on the back of the drag curve, and sink rates near the ground can build up in a way you wouldn't expect from a floaty Warrior / Archer.
- It takes a lot of pull in the round-out, and two-up can run out of elevator, so you may want to experiment with leaving a trickle of power on, especially if slow.
- It has a slightly taller undercarriage and aslightly more nose-down attitude on the ground. So you will contact the groudn slightly earlier than you expected
- It is not a rocket ship, especially in the climb, and your instructor may ask you to select a fairly modest climb power setting e.g. 25" 2500rpm fairly early in proceedings. Be careful not to pull off so much power that you stop going up.
Hope this helps...