Broken clamp – Ropes on your boom can be replaced, but the mechanism needs to work, so check the front end opens and closes smoothly. Check clips at the back end still work and show no signs of damage. Cleet at the back isn’t worn.
The best system is a loop-loop-go, if it’s on of these and working, you’re onto a winner.
Boom grip – You don’t want damage on the boom grip, especially where you will be putting you hands. BUT you can regrip a boom. Buying a tatty carbon boom could be a good thing, you could get yourself a bargain because it looks very worn, but it’s not actually too expensive to regrip a boom. Especially in bigger booms the quality of the boom makes a difference, i.e. you want a good carbon one. In smaller sizes you can get away with something a little weaker.
If you have the time – make the most of the second hand market. Find an old, tatty carbon boom and give it a complete overhaul. For bigger sails you’re going to want a stiff carbon one, if you can sniff out a bargain (these are expensive new), and you’re willing to do the work i.e. re-grip, new cleets, new clamp, you could get yourself an amazing boom at a rock bottom price.
Buying the right mast for your sail makes a massive difference. Keep within the brand, don’t mix and match sail and mast brands. In general terms even an older mast from the same brand should work well.
Go for highest carbon content you can. It will give you a crisper, lighter, more responsive feel and give your sail more wind range. This applies even more to large RDM masts – if you’re freeriding with an RDM masts these might not be as good as SDM in bigger sails. For big freeride go SDM with as much carbon as possible.
Avoid any obvious signs of damage at the join the mast, signs of splitting and any cracks anywhere on the mast.