Basic/simple example of abstract base models and multiple inheritence...

models.py

# ...

######################################
## 
## Abstract models:
## 
######################################

class Base(models.Model):
    
    # http://code.google.com/p/django-tagging/
    tags       = TagField()
    categories = models.ManyToManyField('Category', blank=True, null=True)
    created    = models.DateTimeField(_(u'created'), editable=False)
    modified   = models.DateTimeField(_(u'modified'), editable=False)
    
    # Need this here otherwise tagging will trump with its own manager:
    objects = models.Manager() # Admin uses this manager.
    
    class Meta:
        abstract = True
    
    def save(self, *args, **kwargs):
        if not self.pk:
            self.created = datetime.datetime.now()
        self.modified = datetime.datetime.now()
        super(Base, self).save(*args, **kwargs)
    
    @property
    def is_modified(self):
        return self.modified > self.created
    
tagging.register(Base)

class Person(Base):
    
    # ...
    
    class Meta:
        abstract = True
    # ...
    
    def full_name(self):
        return u'%s %s' % (self.name_first, self.name_last)

class Athlete(Person):
    
    # ...
    
    class Meta:
        abstract = True
    # ...

class Staff(Person):
    
    # ...
    
    class Meta:
        abstract = True
    # ...

class Place(Base):
    
    # ...
    
    class Meta:
        abstract = True
    # ...
    
    def save(self, *args, **kwargs):
        # If latlng has no value:
        if not self.latlng:
            # Add + between fields with values:
            location = '+'.join(filter(None, (self.address1, self.address2, self.city, self.state, self.zip, self.country)))
            # Attempt to get latitude/longitude from Google Geocoder service v.3:
            self.latlng = get_lat_lng(location)
        super(Place, self).save(*args, **kwargs)
    
    def get_lat_lng(self):
        if self.latlng:
            return self.latlng.split(',')

class Event(Base):
    
    # ...
    
    class Meta:
        abstract = True
    # ...

######################################
## 
## Models:
## 
######################################

class Season(Base):
    # ...

class Conference(Base):
    # ...

class Team(Base):
    # ...

class Coach(Staff):
    # ...

class Player(Athlete):
    # ...

class Schedule(Base):
    # ...

class Game(Event):
    # ...

class Stadium(Place):
    # ...

class Page(Base):
    # ...

# ...