Hello Graham,
As Peter wrote, I too use ratchet blocks for the sheets, attached well aft, and a tack line led back to the cockpit. I fitted extra clutches so that I can use one for the tack line.
If you use a snuffer, as I do, I recommend also taking the snuffer lines to the end of the pole/sprit and from there back to the cockpit. It allows much more control of the snuffer and it also allows the snuffer lines, tack line and sheet to be worked together, easily by two people and even by one. I use my asymmetric spinnaker singlehanded with this arrangement - albeit in lighter winds than with crew. It takes the risk out of gybing too, since I can simply part-snuff it as I ease the sheet and without leaving the cockpit.
To lead the snuffer lines and tack line, I use a double block with becket at the pole/sprit end, attached by a soft shackle.
Having described how well the set-up works, I share Peter's problem of usually messing up the rigging of it, especially at the start of a season! It would be greatly eased by having a split pulpit. As it is, the block with the tack line (and snuffer lines) has to be passed over the pulpit before being connected to the pole/sprit; the tack and snuffer lines must then be routed through the pulpit on opposite sides and led back to the cockpit (under the jib sheets!). The lazy spinnaker sheet must be led outside of everything, including the forestay, from the clew round to its ratchet block. I use the 'inside gybe' option, leading the sheets over the pole/sprit, aft of the spinnaker tack - otherwise the lazy sheet can drop down under the bow and disappear under the boat (tried it, done that!). While rigging the spinnaker, it helps to have the jib unfurled either fully (i.e. sailing!) or partly (i.e. don't fully furl it in preparation for launching the spinnaker) - that helps keep the jib sheets out of the way and more obvious, as well as guarding against a wrap around the forestay.
I hope that helps and you enjoy your asymmetric spinnaker - it's great fun!
Anthony Russell
235/02 Sea Wyche