The rules on how to identify magic items without spells are also a bit hazy, intentionally, to allow for GM privilege. The spells make things much clearer, and are therefore more reliable if you're not sure how your GM will rule.
In general terms though, in games I've played in the past:
Without any magical aid, one can generally determine whether or not a specific item has magical properties during a rest. One can determine the simple functions of an item through experimentation during that time. If the item must be attuned, then you must attune to discover its functions in this manner, with all attendant risks. Certain functions may require words or actions that aren't obvious, and can't be easily discovered via experimentation.
Detect Magic can immediately (after being cast) verify magic effects, including magic items but not limited to magic items. It gives a bit more information about the nature of the magic as well, giving the astute some hints as to its function. It doesn't require a short rest to use, nor does it puts the caster at any risk (other than the effects of overwhelming auras, I believe).
Identify (which does require a pearl, but the pearl is not consumed in the casting) reveals all functions of a magic item, without requiring attunement. The item must be handled, but doesn't have to be -used-. Functions that require keywords or specific actions are also revealed. Curses or hidden effects are also revealed, though handling the item may invoke them as well (depends on the specific effects).