25 to 30Nm sounds about right as does Eklipse's "old school" 1/4 turn (I like old school!). Torquing spark plugs gives me a problem because, and yes I know it's controversial, I like to apply a light coating of copper or aluminium anti seize grease to the threads before installation. This, of course, makes the threads "slippy" so makes a nonsense of using a torque wrench because you will over tighten and possibly strip out the threads. So why do I do this? because I've come across enough seized in plugs in my time to know I don't want to have to deal with one in the family vehicles. I've never had one of my greased plugs seize.
So tightening without a torque wrench? Well, for me, not a problem as I've been doing it for the best part of 50 years and I've developed a very good "feel" for what the correct tightness is. I can't transfer that to you here but I can make this suggestion. Take a standard new spark plug (the type with a crush washer) like are used in our FIRE engines and install it carefully (because you don't want to cross thread it believe me) twisting it into it's hole by at least a couple of turns by hand before you go anywhere near it with your socket and "T" handle/ratchet. Run it right down the thread until it just "snugs" the washer firmly up between the shoulder on the plug and the surface of the head. This is the point at which you need to exert considerably more force to tighten it further.
So now let's think about what we are trying to achieve here? We want a gas tight seal between the head and the plug. This is where the "crush" washer comes in. Correct tightening of the plug will cause this special washer to "crush" down and take up any slight imperfections between the shoulder of the plug and the face of the threaded hole you are screwing it into. (you did clean up the facing where the washer contacts the head didn't you? Well done if you did because many don't and if you don't you risk damaging this face and failing to achieve a proper seal) As long as you have a reasonable sense of "feel" in your hands/fingers you can feel this crush happening. So, if we go back to our plug which we've just run into it's hole to the point where it's just "pinching" it's washer, if we now start tightening further you'll find it takes a bit of force compared with when we were just "running" the plug down the hole but you'll go about another 1/4 turn or so needing to apply only moderate force. This is the "crush zone" where the washer is being "squashed". It can be a little alarming the first couple of times you do it because it feels quite like a threaded fixing feels when it's stripping it's thread and your natural reaction is to stop tightening! As you continue to tighten into this "crush zone" you will then find the plug will suddenly get really tight to turn - stop immediately! Congratulations, you've successfully crushed the washer and your plug is now correctly installed!
Back in the days when I taught basic mechanics I had a number of old cast iron heads bolted to a workbench and all my students learned this way to install plugs. There are other types of plug (taper seat) which don't use washers so you can't use this method with them but once you have the "feel" for how tight a plug should be you can install pretty much any spark plug with just a socket and "T" bar. (going by Eklipse's 1/4 turn method you would be going an 1/8 turn with a taper seat) Of course this "feeling the crush" method only works with a new plug which has a new uncrushed washer. So if you are reinstalling a used plug it's even more useful to have developed "the feel". I found this especially useful when I worked on DAF cars where the air cooled engines used a very short reach plug which was easily stripped. (we did a fair trade helicoiling plug holes in them for other garages!) Older lawn mower engines are also quite notorious for it too as their "flathead" engines used very short reach plugs which are often stripped out by hamfisted gardeners.
Lastly can I just say, try doing up a few plugs, or even nuts and bolts, to 25Nm with a torque wrench, then undo them again. They don't feel all that tight do they? In my experience a lot of plugs are needlessly over tightened when installed. It's the crushing of that washer which is the important factor. (unless of course you have taper seat plugs - I don't think Fiat are into them are they? - in which case its firmly seating the taper which matters. But again it doesn't need to be "super tight"). Ideally you should always fit a new uncrushed washer every time you reinstall a plug - you can buy them in packets - but not many people bother. Need I say that if you decide to have a go at this and "mess up", as our American cousins would say, don't come crying to me please. It's all a matter of feel and that's impossible to teach from a distance.