Hotel & airline loyalty cards. How can I benefit from these if I'm doing the booking, but not the travelling?

I spend all day booking flights and hotels for classical musicians who all have frequent flyer cards and hotel memberships but there must be schemes where I benefit from choosing these airlines, or hotels for my clients. ANy ideas?

There is no way to capitalize. You must be the person either traveling or staying to get the points/miles.

Best thing to do is get a credit card like CitiBank AA Advantage credit card and use it to pay for the purchase of airline tickets for these people, then bill them directly. That way, you earn airline mileage points for yourself. Check out these type of airline affiliated credit card offers.

However do NOT be suckered by the CitiBank offer of a "free companion ticket" !! The airlines USUALLY have a better offer than that offer, no matter how you pay.