There is a greyed out prompt on the telephone key which has the +61 etc (whilst in AU) and there are some validation tools in different editors (ID, JOSM etc) and there are also apps that can make it slightly easier for specific tags but phone tagging is quite complex world wide. I just use an Overpass query to find common issues and correct them (Australia only). There are only a few each day so its not that onerous and it helps new mappers to get on top of the tagging early on in their map careers.