Create a context processor

settings.py

TEMPLATE_CONTEXT_PROCESSORS = (
    'myapp.context_processors.user',
)

context_processors.py

def user(request):
    if hasattr(request, 'user'):
        return {'user':request.user }
    return {}

user is now available in any template:

{% if user.is_authenticated %}Do Something Special{% endif %}

source: stackoverflow

Every once in a while you need some old fashion SQL style queries in django.  This is a common one for reporting and aggregation.  Its fairly easy to replicate in a queryset.  Say I wanted to get the authors and the number of articles they have written going back to the beginning of 2009 to the present:

from django.db.models import Count
Article.objects
.filter(created_date__gte=datetime.datetime(2009,1,1))
.values('author')
.annotate(Count('author'))

The result:

[{'author__count': 1028, 'author': 17L}, {'author__count': 9, 'author': 9L}, {'author__count': 39, 'author': 12L}, {'author__count': 581, 'author': 10L}, {'author__count': 15, 'author': 7L}, {'author__count': 366, 'author': 13L}, {'author__count': 233, 'author': 5L}, {'author__count': 167, 'author': 15L}, {'author__count': 287, 'author': 14L}, {'author__count': 10, 'author': 6L}, {'author__count': 2101, 'author': 16L}]