How contribute with a patch

[VETSEL Patrice]

I'v made some researches but i can't found any informations.

I want to help ubuntu team by creating a patch to a package (2 in facts ;) )
Reporting a bug i want to help developper by give him a patch to his 
package (because i know the solution).

I do :

apt-get build-dep package
apt-get source package
cd package

I make my modifications in sources files.

What are the commands i must invoke to finish the process  ?
What do i send as attachment in reporting bug in launchpad ?
I must precise that i do not have gpg key.

Regards