From OpenStreetMap Wiki
Basically a collection of OpenStreetMap- and mapping-related tips and suggestions (for future reference).
- Please do not mass-delete other contributors' contributions [To make way for data imports]. Data added by people who know the area is usually better than anything imported. If you want to import data, it is your responsibility to carefully integrate it with what is already there - not rip and replace! (Based on 1)
Note: some are taken from Names#Notes
- Don't abbreviate words (like St. for "Street" or "Saint", "Ave." for "Avenue", etc.)
- Use mixed case with the first letter of each word capitalized (for example, Church Street, not Church street)
- Name is the name only. It should not include categories, types, addresses or notes. Any addition information should be included in separate tags to identify its meaning (like note= and description= )
- Small drainage ditches (called "canals" in the Philippine context) should be tagged as waterway=ditch, not waterway=canal.
- Do not split waterways just because they are under a bridge.
- Tag them as disused:amenity=* if previously tagged as amenity or disused:shop=* if previously tagged as shop. Change the tag from name=* to old_name=*.
- If a new amenity or shop replaced the disused amenity or shop, change the tags immediately (from disused:amenity=[old amenity type] or disused:shop=[old shop] to amenity=[new amenity type] or shop=[new shop type] and remove the old_name tag.
- Do not delete them, since they may be used in the near future. Mark them as access=no. Examples: and
- When it's (already) on the map as a polygon, do not add it as a node. Your edits might confuse other mappers and OpenStreetMap end-users.
- Do not use designation=* for classifying various features like schools. The tag is originally used for recording the legal classification of a certain way (footpaths, cycling paths, etc.) or "various levels of nature reserve and protected areas of countryside" in the United Kingdom.