ALL of the level affecting levers (except barrel blowing, which always affects the entire level) announce themselves through a level feeling. You can use that to determine whether pulling one would be a good idea.
If one of those level feelings occur and you only find 1 lever on the entire level, it's pretty definitive what it'll do.
Other than that, it's guess work, but the odds are slightly in your favor in terms of good effect versus bad effect.
There's a 8 out of 17 chance the lever will do something good. (Heal you, repair armor, flood with water, or kill enemies)
There's a 2 out of 17 chance the lever will do something that could good but could be bad. (Blow all the barrels in the level)
There's a 7 out of 17 chance the lever will do something bad. (Flood acid, flood lava, summon enemies, or destroy the walls)