Here's what works for me. It assumes a 6-foot tether and uses three hefty D-rings with large washers as backing plates.
The key D-ring is on the cockpit bulkhead, an easy reach when standing in the companionway. You clip in from below, then climb up. The full-length tether reaches everything in the working cockpit, from cabin house winches to steering gear on the stern. I never unclip until safely belowdecks.
For going forward, D-rings are mounted on the aft cabin house top. The jacklines run from there to bow cleats, on either side, inside the shrouds. To go forward, double the tether to reduce its length.
I use 1" blue webbing from Sailrite, rated at 2400 pounds or so. I suppose the yellow is stronger, but chafe is the issue not breaking strength, and UV not a problem because nobody leaves them baking on the deck.
Lots of ways to do this, the key is to set it up so it actually gets used.
The most important issue: no possible use of the system should allow you to trail off the stern of the boat, and the tether should never be attached to anything but its dedicated fitting or jack line.
And, oh yeah--jack lines aren't designed to keep you on the boat, but rather attached to the boat if you get tossed off. I rig dock lines in loops from the topsides when offshore to facilitate climbing back aboard over the windward side.