What size hook would you recommend for a NEKO rig with a 6 inch stick worm? It seems my hook up ratio is not very good and I am new to NEKO rig fishing. Any advice would be appreciated.

I use a 1/0, Make sure the hook is threaded through the bait or O ring facing the tail.

Ski provided good information - the VMC Neko hook may be the most popular ; use a 1/0 size for a 6" stick worm , for a 5" stick worm use a #1 size and for finesse worms use a #2 size : VMC Ike Approved Weedless Neko Hook 5pk - Tackle Warehouse (*if zero weed concerns - use the standard VMC Neko hook : https://www.tacklewarehouse.com/VMC_Ike_Approved_Neko_Hook/descpage-VMCNH.html