I have three top level objects, all objectClass=nisMap:
Then under auto.master there are two objects with objectClass=nisObject:
Only the home entry is "required", the other is for a mount at /groups which I was using for ... group directories.
Under nisMapName=auto.home there are all my user directory objects which all have objectClass=nisObject:
Where the first one is for "all users" and the / and & are wildcards for the username which doesn't match any other entries in the map. So a username "tom" would be mapped to "nfsservername.com:/full/path/to/real/files/tom" if he didn't have a separate entry.
The group objects are all children of nisMapName=auto.groups and are similar in content to the ones shown above.
I didn't put this in LDIF format and I assume you know a little about LDAP already, so if not I can expand a bit I suppose.
A nice project that makes dealing with LDAP a lot nicer is http://lam.sourceforge.net/
I liked it enough I got his commercial offering, but the open version is very helpful for administration.