hook_form_alter() and hook_nodeapi() to alter fields and insert additional data on insert
As mentioned in the comments any extra fields you add to to a node form won't automatically be persisted to the database, the node module only takes care of the fields that it knows about.

Traditionally there are 2 options:


Use CCK instead and add fields to the node that way. Then you don't need to take care of data storage/loading yourself.
Add your own table for data storage using hook_schema(), making sure you have a column for nid (node id). Then in hook_nodeapi() use the insert and update ops to run a db_query() to insert/update the data in that table for the current node.

Then you just need to load that data back from the DB on to the $node object in the load op of hook_nodeapi(). Your data will then be available at $node-&gt;field_name when you have a node object loaded with node_load().