There are various ways on how to tag housenumbers using the widely used Karlsruhe Schema. One way to tag housenumbers is to associate house/s and street/s using a relation. Another is to add address tags on the object (node/way) itself.
Tags
Using associatedStreet method
Key
Value
Notes
type
associatedStreet
name
name of street
adding name in the relation is optional but recommend
VERY IMPORTANT:NEVER add the name tag (name=*) on the housenumbers. Nobody wants to know where you live, where your friends live, where you did it (don't ask me what "it" is), where some you know lives, or where your favorite celebrities live. Because there are people who are paranoid about their security.
Try to map housenumbers during siesta time (1-4 PM), since a good percentage of the populace are tired and sleepy. Especially in places where locals are known for their violent behavior. Don't map housenumbers between 10 PM and 5 AM (local time)
Have an identification card (and OpenStreetMap promotional materials) to prove (to certain people, especially occupants and local officials) that you aren't a crook/thief scouting for houses to loot or a "stalker".
If necessary, coordinate with the local authorities (preferably with barangay officials) before mapping, especially if you’re gathering “sensitive” data like housenumbers. this will lessen their suspicion.
Notes
Housenumbers vary from jurisdiction to jurisdiction. Examples can be found on the table below.
Housenumber examples
Place
How they apply it
Example
Los Baños, Laguna
Except for some poblacion barangays, Mayondon, Batong Malake and possibly Bagong Silang, All barangays in Los Baños use two housenumbers - one assigned in the early to mid-1990's and another assigned in the late 2000's.
Paete, Laguna
The ref of the barangay (01 to 11) and the actual housenumber