There are several editors available for mobile phones. Mapzen POI Collector is an application available for both Android and iPhones. Mapzen is aimed to be easy to use and make it easy for ordinary people to start mapping easily.
Vespucci is an application for Android phones that can be used for GPS point gathering and basic OpenStreetMap editing. It is aimed at more advanced users, as you need to know the tagging scheme used.
Mapzen is available from both the Android Marketplace (https://market.android.com/details?id=com.mapzen) and the iTunes Store (http://itunes.apple.com/gb/app/mapzen-poi-collector/id338079717?mt=8). When you enter an area that you want to you open the app and the map will open in the location that the map was last shown. To get to your current location you select the android menu, and choose My location. The screenshots here are taken from the Android version of the App. The iPhone version is similar.
Mapzen is focused on simple editing of points of interest (POIs). The current set of POIs will automatically load. You can select a POI to get more info about it by tapping the little blue arrow.
Editing a current point involves selecting a point and going through the menu system to change the properties of it, and then finally saving it.
We did not go very in depth into Mapzen POI Collector, because the application is intended to be intuitive.
Vespucci is an advanced editor that allows you to update the OSM data in the field. Refer back to the JOSM section to understand tags. You also need to know about the OSM data model (a chapter in this book) and the tagging scheme which is described on the OSM wiki on the Map Features page: http://wiki.osm.org/wiki/Map_Features. You currently can't edit relations with Vespucci.
You can download Vespucci from the Android Market by searching for "Vespucci" or going to the following page (https://market.android.com/details?id=de.blau.android), and following the usual installation procedure for your phone.
To be able to edit OSM data you need to enter your OSM username and password into the settings.
Once you are in an area you need to start the app, get your current location and download the current OSM data for the area.
Screenshot showing a GPS track with the underlying OSM data.
You can move the map around when you are in move mode by dragging the map around. There are zoom in and out buttons that allow you to change the zoom level. You can also use the pinch gesture to zoom in and out of the map.
Once you have made some changes to the data in the area you will want to share those with the rest of the OSM community.