All of the above mentioned methods will work. I have a M1952 M/S & it always makes me a bit nervous to unset the trigger on a live round. xausa's method is probably the safest but unless the rifle has no scope or the scope is mounted extremely high there is not enough room under the occular end of the scope to engage the wing safety.
All of the post war M/S rifles have either a side safety or a tang safety in addition to the wing safety which will (in theory) prevent the rifle from firing set or unset if the trigger is pulled while engaged.
What I do to unset the trigger when loaded is to engage the side safety & then with the rifle pointed in a safe direction open the bolt & remove the cartridge in the chamber then with the bolt still open use Kutter's method of unsetting the trigger. Alternately you can also simply pull the front trigger to unset it with the bolt open & chamber empty but this puts more wear on the trigger system.
The magazine is best unloaded by pushing the button on the right bolt rail.
All in all the Steyr M/S is a neat & well made rifle & mine (a .270 WCF Stutzen) is very accurate but I still prefer to hunt with a Mauser 98 or Winchester Model 70 & w/ a good single stage trigger.