I'm playing with a DM that usually makes us encounter strong enemies in the middle of nowhere. That's fine since we can choose to fight or not, but the real challenge is determining how strong the opponent is so we don't die a miserable death. If the enemy is a beast, it's fairly easy to determine the encounter's difficulty, but, when it comes to spellcasters, it's hard to determine how difficult they'll be to take in a fight at a glance. I tend to look for items the enemy has for hints, but that's not very effective.
Is there another way (or, at least, a smarter way) to determine an opponent's level or how strong it is?
The party is a human ranger, human paladin, half-elf rogue, and elf necromancer. All are level 5.
First of all, thank you for the comments, questions and advises!! I think RPG is great because of discussions like this one! I came with some conclusions myself after reading everything you guys posted, but there's a background here I think I should share with you guys before start it. Me and my party had this 1-year-long campaign that ended tragically after a silly bar-fight against high-leveled guys we came to encounter and occasionally didn't know their reputation. In fact the DM alerted us about the danger, but it doesn't seemed something deadly.. at a glace. That was fast, and painful. But it was our fault.
Since that episode, I've been trying to be more careful and think before engaging into senseless fights. So I thought it would be helpful to be able to check the level of the threat before we choose to do something (something we see in movies or cartoons when the opponent emanates something like an dark aura...). And after hearing from you guys and talking with our DM I end up concluding it's just not fun to be able to control situations in that way. Like some of you guys wrote above: the best way to approach this "problem" is by role-playing (talking, looking, interacting) and perhaps that's why abilities like Know Your Enemy and Insightful Manipulator are made for more leveled players. Such a way to check the opponent is not as easy as it might look like and that makes sense!
By the way, the threat my party encounter yesterday (the reason why I wrote the question) end up been something beatable! By having the conversation with the NPCs, we decided to fight and that was actually part of DM's plan to make us choose to change the course of the history or not.
Thank you again!