Right, setting up coilovers. I do this on race cars (Clio's) so the set-up is slightly more critical, but the basics are the same.
Start with all the platforms at the bottom and adjust from there. Count the number of turns, and make sure each strut has the same amount of turns applied. You will then get a uniform height all round.
Doing it by eye or measuring from wheel arches to tyres isn't very reliable as you are unlikely to have a completely flat floor and body panels, etc are often not straight/level. If you do it by eye you are likely to get very strange corner weights...
Coilovers give you the opportunity to move weight from corner to corner to change the balance, handling and tyre temparatures/wear. As I said at the start it is move critical on race cars but will affect a road car too.
Basically, if you raise the height of the rear right, it will transfer weight onto the front left. This may cause your car to understeer, alot and will make the tyre overheat! Conversely, if you raise the front corners, it will transfer weight onto the opposite rears. This may cause lack of grip at the front in high speed corners, and a serious amount of weight transfer during braking.
If you move each platform an equal amount of turns you shouldn't be too far off. You could get the car professionaly 'corner weighted' on a flat floor to ensure it is all working effectively....
