If you should list 3 typical behaviours that show weakness and 3 typical behaviours that show strenght in an opponent, which would you say were most universal and easy to spot?

None are universal. Furthermore, all are situational. The subject cannot be simplified in the way you are trying to do it.

Proskiller, you posting history tells a story that you have limited poker experience...so possible you are asking the question here for suggestions about what you need to pay attention to at your local home game or casino. Since you "may" be of limited skill, I suggest you start with one....use and abuse for 100s of hands.....before moving on.

The one often suggested is:
weak means strong; strong means weak.

I prefer:
Look for behavior differences. A normally chatty guy may clam up with a polar range (nuts or bluff). A quiet guy that pauses to tell a "story" before he bets...usually has the nuts.....especially if the bet sizing is larger than table "normal".

I wasn`t thinking about tells that are 100 % universal, those clearly don`t exist.

But more like for example that holding ones breath is a more often than not a sign of bluffing.

I think they are really situational for each one. For instance, a lot of people I play with live mistake my legs shaking as some sort of tell. But my legs mostly shake because I have constant nerve pain, and moving them around kind of helps it.

I just read a post on here which listed 4 really good signs you should know. Have a look at this thread: http://forumserver.twoplustwo.com/24...tells-1665181/

I'm sure it will help

I'm sure there's LOTS of answers here, but I'm going to go with players who try to look away or otherwise try to disappear before the action gets to them. You can automatically fold your speculative limps.

The disappearing act is a classic.

Also, to King's Spew point, the opposite tell is usually visible in an opponent who exhibits the tell, so if they threaten with chips they are trying to make their presence known, though in the pre-flop scenario I'd expect the disappearing act, and perhaps post-flop with some action when they are drawing I'd expect the more threatening nature.

I think the threatening nature usually comes when they do not want to face a tough decision, and want to deter that from happening.