class Tag(models.Model):
    tag = models.CharField(max_length=50)
    quanity = models.SmallIntegerField()
    
    def __unicode__(self):
        return self.tag

class Post(models.Model):
    author = models.ForeignKey(User)
    date = models.DateTimeField()
    title = models.CharField(max_length=100)
    post = models.TextField()
    tags = models.ManyToManyField(Tag)
    
    def __unicode__(self):
        return self.title
    
    class Meta:
        ordering = ('-id',)

class Post(models.Model):
    author = models.ForeignKey(User)
    date = models.DateTimeField()
    title = models.CharField(max_length=100)
    post = models.TextField()
    
    def __unicode__(self):
        return self.title
    
    class Meta:
        ordering = ('-id',)
    
    def _get_tags(self):
        return Tag.objects.get_for_object(self)
    
    def _set_tags(self, tag_list):
        Tag.objects.update_tags(self, tag_list)
    
    tags = property(_get_tags, _set_tags)

from tagging.fields import TagField
class Blabla(models.model):
    ...
    tags = TagField(blank=True, null=True)

Error: App with label core could not be found. Are you sure your INSTALLED_APPS setting is correct?