Setting permissions to new files?

[Bruno Buys <bruno.grupos@gmail.com>]

Where do I change the permissions that are set when I create a new file? 
I mean, I'd like to be able to change the default permissions that my 
system atributes to new files.


bruno@merlin:~$ > newfile
bruno@merlin:~$ ls -l newfile
-rw-r--r-- 1 bruno bruno 0 2007-06-17 18:06 newfile


I'd like new files to be created as writable to the group, as in

-rw-rw-r-- 1 bruno bruno 0 2007-06-17 18:06 newfile


thanks!