Prerequisites

• Java (probably already installed)
  https://java.com/download
• Download JOSM at http://josm.openstreetmap.de
  (use josm-tested, or use web starter)

Always checks for most recent version on startup

• Download new one if needed. Update plugins.

Preferences

• Enter OSM username and password
• (optional) Add plugins
• (optional) Add additional imagery

Recommended plugins

• EditGPX (if you'll be working with GPS data)
• Field Papers (low-tech surveys)
• House Number Tagging Tool (for entering lots of addresses)
• Mirrored Download (for downloading data from OSM mirrors)
• Opening Hours Editor (adding/editing businesses)
• Notes (view/add/edit map notes)

Additional imagery

• More on this later....

Differences from iD

• Work on a specific area at a time
• Faster and more responsive, especially for larger areas
• Plugins for almost any type of task
• More exposure to the "raw" data

Tagging is freeform key/value.

• JOSM has presets.
• Use wiki as reference
  Tip: Add search shortcut in your browser
• No hard rules. Goverened by consensus
• All that is verifiable can be mapped
• TagInfo can be helpful

JOSM has two main tools:

• Select
• Add

Learn and use keyboard shortcuts
(in hovertext)

• S: Select
• A: Add nodes
• Alt-A: Add tag
• W: Improve accuracy
• Q: Orthogonalize
• O/L: Align in Circle/Line

Imagery

• Bing/MapBox satellite (great for tracing roads, buildings, etc)
• Tiger 2013 (street names)
• USGS/MSR Topo (features names)
• MassGIS L3 Parcels (boundaries)