I don't know why this question is under my recommendations, but I'll give it a shot.
I suppose in truth you can never truly tell 100%, but I am a very perceptive person in strange ways. I can learn a-lot about someone before talking to them just from subtle behaviors, personality (how they act around others, how they talk, tone of voice) and body language.
I can almost define a persons character this way and the scary thing is I am usually 90% right.
As for fighters, the few I know seem to have a very confident air about them. They are "proud" in a good way, not egotistical, and do not brag of their exploits. Their eyes though are what get me, always alert, poised, and aware of everything. Nothing seems to escape their eyes. And most I know have outstanding heart and character. They may be learning how to hurt people, but hurting others is far from their mind and they are kind hearted souls full of compassion.
At least those I know of.
You can't tell.
And usually it's the quit ones and smaller guys you really have to worry about. Now with that said you should never discount anyone.
And you're right, a group is something to worry about. So find ways to avoid them, and keep from fighting.
You can't tell if someone is tough or can fight by looking at them. Muscles, height, loud talk--none of it matters. Take a look at the image I've linked in the source. That guy weighs around 160 pounds and would wreck everyone in this thread consecutively and in short order.
I agree - you can't tell. But bullies hide in crowds and behind big mouths. They also avoid those who hang out in crowds and who have big mouths.
When you approach someone - whether they are your best friend or your worst enemy - greet them as if they were your best friend. Look them in the eye. Don't be timid or shy about your speech. Be confident.
Those who are confident hide their weaknesses - including fear - and that scares bullies, because now they don't know whether you can fight or not. They will ultimately find someone else whom they perceive to be a weaker person.
When it comes to fighting you can't judge a book by it's cover.
I can tell you this much.
If you're worried that one of them can fight you're going to constantly wimp out of teaching them a lesson.
Punch them in the nose and then kick them in the groin. You don't have to be strong or have much skill it you fight dirty. Don't be shy, give it a try.
Find the leader and beat him, then the group collapses. Also if you get the leader alone, you can negotiate a settlement or peace treaty, or find out why they are harassing you so you can get them off or threaten them off.
No way of knowing till it's happening. But chances are they have no formal training. Most that do have discipline and they don't seem to.
There's a group of kids that keep harassing me and my friends, they won't stop and it seems like somewhere down the line they may need to be taught a lesson if it continues . the thing is none of us are particularaly good fighters. The group of kids are mouthy and there is one tall one, one small one, one reasonably tall but fattish one and couple of others. Is there any way of telling how good a person would be at fighting and your odsa of winning. I'm concerned that if it does result in a fight the group will gang up on me and jump me.
Sun Tzu -- “Thus it is said that one who knows the enemy and knows himself will not be endangered in a hundred engagements. One who does not know the enemy but knows himself will sometimes be victorious, sometimes meet with defeat. One who knows neither the enemy nor himself will invariably be defeated in every engagement.”
Nope. You can't tell.