Take out the track bars and disconnect or remove the sway bar. Make sure the spring and shackle bushings are good, not age hardened. Make sure the bolts are not so tight you can't spin them with a wrench on the head.
The stock springs should flex well enough (especially with trackbar and sway bars removed), but you'll just have issues fitting larger tires without a lift. Short of going spring over, run a high quality spring (BDS, OME, etc) if you are going to lift it. And I wouldn't run anything over 3.5" of spring lift. The spring arch is increased to provide the lift which hurts its ability to flex.
Having a ton of articulation doesn't necessarily help you out in all situations, either. Running leafs is generally considered to be more stable in certain off camber situations. Yes, you are more likely to lift a tire in twisty sections, but as long as you have lockers, you'll continue to move forward.
Iv heard that yj's dont flex stock and i was wondering if it was true, and if possible someone could give me some ideas on how to get better articulation out of it.
Sway bar disconnect kits are the way to go for off road. Increases the flex a lot when disconnected and keeps it safe with good road manners when connected.
86/00 CJ7 Laredo, 33x9.5 BFG AT's, 'glass nose to tail in '00, 'New' frame,wires and plumbing in '09. Carter BBD Carbed 4.0 HO in '10.
89 YJ Renegade. BBD Carbed 4.0 HO. Locked front and rear with 33x9.5 BFG AT's
Some Canadian Bush Jeep Runs and Build Photos: http://mikeromainjeeptrips.shutterfly.com (10 new albums added Sept 16/10)