Hi Kenny
I think a good start is to settle on one deck for the time being and go through the threads in this forum whilst looking at your own deck. If you come up against anything you don't understand, then ask and someone will always help you out. There is no definitive way to read with a Marseilles deck its experimental, but it really is a good idea to understand the differences between TdM I and TdM II. From there you will instantly (or almost) be able to look at a Marseilles deck and identify it's basis.
Here is a thread to get you started:
http://www.tarotforum.net/showthread.php?t=61489
You have to be prepared to do quite a bit of reading.
There are many different ways of interpreting the cards so I would advise you to read up on all styles (most, if not all, will be posted in these forums) and then try them out. You will settle on one or even devise your own based on the knowledge you have picked up here. Over time you may even develop and/or adapt your own method and style.
I always recommend these threads for working through, and adding to as well. Here you can see a mixture of interpretations for one card:
http://www.tarotforum.net/showpost.php?p=749177&postcount=3
You will find the above post in the Contents of the Marseilles forum.
Enjoy!
Moonbow*