Following the video at http://modulesunraveled.com/organic-groups, I installed og, entity and other modules our coach forgot to mention as necessary, and followed his instructions to create a new content type, "group," and alter the existing content type "article."

Following that, I get these errors: Notice: Array to string conversion in InsertQuery_pgsql->execute() (line 42 of /srv/www/drupal/drupal-7.14/includes/database/pgsql/query.inc). Notice: Array to string conversion in InsertQuery_pgsql->execute() (line 42 of /srv/www/drupal/drupal-7.14/includes/database/pgsql/query.inc). Notice: Array to string conversion in InsertQuery_pgsql->execute() (line 42 of /srv/www/drupal/drupal-7.14/includes/database/pgsql/query.inc). Notice: Array to string conversion in InsertQuery_pgsql->execute() (line 42 of /srv/www/drupal/drupal-7.14/includes/database/pgsql/query.inc).

There were others earlier, just hang on while I retrace, OK?

I deleted "group," two of those messages are gone. I delete two og_ fields from "article," the other messages are gone.

Ok, it's taken a while, but I've disabled and uninstalled all the og, entity and views modules I installed earlier, so let's try again.

Modules. Enable Organic groups 7.x-2.0-alpha3+10-dev

Save Yes, enable Entity Reference

Oh crud:

FieldException: Attempt to create an instance of field og_membership_request on bundle og_membership_type_default that already has an instance of that field. in field_create_instance() (line 490 of /srv/www/drupal/drupal-7.14/modules/field/field.crud.inc). The website encountered an unexpected error. Please try again later.

I think first time round I had SQL errors. Careful readers will have noticed I'm using postgresql.

in each instance, I chose the -dev versions, this is a development site;-)