The documentation in http://forge.jboss.org/docs/using/basic-javaee-app.html omits critical details.
1) In section "Set up persistence (JPA)", useful values for "

" and "

" are not provided. From slopping around, I found that "HIBERNATE" and "JBOSS" worked.
2) While trying to follow section "Deploy/undeploy to AS7", issuing the command "forge install-plugin jboss-as-7" yields the error:
**ERROR** Exception encountered: no default repository set: (to set, type: set DEFAULT_PLUGIN_REPO <repository>) (type "set VERBOSE true" to enable stack traces)
At one point in the documentation, I founnd what the value of <repository> should be, namely https://raw.github.com/forge/plugin-repository/master/repository.yaml – however, I don't think this is the correct value, as the command then proceeded to mangle the value, changing the .yaml to yaml.yaml