It is in fact very simple as FTM 2012 will recognise your FTM 2006 file and offer to make a copy of the file and convert it to FTM 2012 format.
Here is a a summary of the steps
I assume that you are going to install FTM 2012 on the same computer as your FTM 2006?
Open your FTM 2006.
Go to Tools>Compact and compact the file. This puts it in the best possible shape for conversion to FTM 2012 file format.
Make sure that you also have a good backup of the file.
Close FTM 2006.
Note you don't have to uninstall FTM 2006 from your computer for the next steps.
Install FTM 2012 from the application CD
It is usually an auto start job and follow the prompts
When FTM 2012 first starts, it may detect a patch (there have been two patches) and offer to install the patches. You should do this.
When FTM 2012 is installed go to Help>About and it should show version 21.00..506. The .506 is the key bit.
Note you also have to register FTM 2012, which is different from activating an Ancestry subscription. If you are already an Ancestry.com subscriber, use your user name and password when you register FTM 2012 otherwise create a new account.
FTM 2012 should detect your FTM 2006 file (a file ending in .FTW) and offer to convert it. You should accept this.
If it doesn't detect the file, from FTM 2012 go to the Plan View>New tree>install from an existing file.
Navigate to where you have your FTM 2006 file saved , select it and continue.
That really is about all there is to it.
You will have a bit of a learning curve from FTM 2006 to FTM 2012
In the help section there are some very useful tutorials and also a 360 page Companion Guide as a PDF file.
I have also provided you with a few useful links. The webinars in particular are very good.
FTM 2012 Support: http://www.familytreemaker.com/Support/
FTM 2008/9/10/11/12 Knowledge base:http://ftm.custhelp.com/cgi-bin/ftm.cfg/php/enduser/std_alp....
FTM up to 16 Knowledge base and support: http://past.familytreemaker.com/help/default.aspx
FTM-Tech (Where all the high end users hang out):http://lists.rootsweb.ancestry.com/index/other/Software/FTM-...
Ancestry.com- FTM- another help posting site:http://boards.ancestry.com/topics.software.famtreemaker/mb.a...
Ancestry.com- Online Family Tree, My Canvas, FTM, etc:http://ancestry.custhelp.com/cgi-bin/ancestry.cfg/php/enduse...
Ancestry.com Blog –Great site for help on online matters:http://blogs.ancestry.com/ancestry/