these guides are good:
http://www.badgermotorsport.co.uk/lowering.htm
http://www.suzukituning.com/PSA/Suspension/Lowering.htm
and here is some info from me:
firstly take the shocks off so that the suspension arms dont have any pull on them apart from there own weight, then do measurements (measure from behind the hub to the bottom of the car & note measurments)
Then undo the ARB plate bolts so u can rotate the ARB out the way, next u need to remove all the torx bolts and offcenetered washers from both ends of both torsion bars
now get some WD40 and cokacola and plater it around the ends of the torsion bars and splines this will help eat into the rust and help free it off
then you can either try slide hammering the torsion bar out if its still seised in you can try the bolt and socket method as shown in the pic below (make sure that the bolt has at least 10-15mm in the torsion bar before pulling out or u will rip the threads)
socket and bolt method
if its still not budging then you can get a mate to hit the other side of the torsion bar with a 7lb lump hammer and a bar with you slide hammer or socket and bolt the other side, the pressure of both forces against the torsion bar normally frees it up
lump hammer and bar:
if its still not budging then u can use a blow torch to heat the ends around the torsion bar up as the metal expands it normally healts to break the seal of the rust and help free it up
also sometimes if u put a jack under the arm ur trying to remove the torsion bar from and jsut tkae it up a few mm it helps take a little weight off the torsion bar which can help it have less stress to come out. u can keep applying WD40/coke mixture throughout the different stages to try help it and just have to keep trying, they will give way eventually
once done and out measure and use a jack to hold the arm at the new height u want and then pop the torsion bar back in, and fit everything back on, do some for both sides, job done
here is also a animated pic i made showing torsion bars
