Numbers are usually what we are looking for. Coordinates. A pair, north and east. Sometimes also a bearing, although here you still need a point from which to take a bearing. Usually this is the coordinate where the listing was placed.
If a coordinate is hidden, then either in its entirety and the degree-decimal-minute notation that is common in our country (e.g. N 52° 12.345 E 009° 59.876). Or as a subset of it. Maybe only the last 3 digits of north and east (in which case, unless otherwise specified, the listing coordinate includes the missing coordinate parts), often it is the last 5 digits.
For those who want to confuse the puzzlers, other coordinate formats are used, e.g. decimal representation. Which would turn the above example into this notation: 52.20575 9.997933. Expressed in degrees, minutes and seconds: N52° 12′ 20.7″ E9° 59′ 52.56″ . Great for confusion when the mystery solver has too much focus on the supposed coordinate in the usual notation. Converters to the coordinate formats for this can be found on the internet and in almost every major geocaching app for on the go.
So much for what we are looking for. Now for how we can find it. The chapters on this will inevitably keep overlapping, so please don’t be surprised.