I'm playing with this DM that usually makes us encounter strong "enemies" just in the middle of nothing. That's fine, since we can choose to fight it or not. But the real challenge is to find how strong the opponent really is, so we don't die a miserable death. If the enemy is a monster, it's kinda easy to say the difficulty of the encounter. But when it comes to spell-casters, it's a bit difficult to tell from a first look. I always looked for items or other possessions the enemy may be using and try to make it a hint, but it's not very effective.

Is there another way (*at least a smarter one*) to check the opponents level or how strong it is so we can make smarter choices in encounters?

My party:

 - Human, ranger 5lv
 - Human, paladin 5lv
 - Half-elf, rogue 5lv
 - Elf, necromancer 5lv