Migrate django1.2 project to django1.4
This is what we are doing (we're upgrading ~60Kloc from Django 0.97 to 1.4):

create an upgrade branch of your code
create a virtualenv for working on the upgrade
download the "next" version of Django (if you prefer small steps), or the Django version you want to end up with, and place it into your own version control system (VCS).
check out Django from your VCS to the root of your virtualenv.
repeat until done:

run your testsuite (and coverage).
fix any problems

add a comment in your root __init__.py file indicating which Django version your code works with (this will save you a lot of time one day :-)
merge your trunk out to your upgrade branch (to get all the changes that have happened while you were working on the upgrade).
run your testsuite, fix any problems, then check-in the merge.
finally: reintegrate your upgrade branch back into trunk.

Now you've upgraded your code (you'll still have to plan the deployment of the upgrade, but that's another question).
ps: we store Django in our VCS so we can keep track of any changes we need to make to Django itself (especially needed if you don't want to go to 1.4, but still might need one or two fixes from that version).
We developed project with django version 1.2 and python 2.4. Now we want to migrate the projects into latest version (Django1.4 and python2.7).
I am very new for migration, Can anyone please advise on this. 
What things do I need to take careof?
Do we need to rewrite all the code again?