My last advice is try to go as fast as you can LOL. It is odd, but the faster you go, the easyer it is to quilt. And just keep trying. It is one of those things that only gets better the more you do it.
I heard that too and while it works for some people it did not work for me. I had to slow down to get more even stitches.
I like this video: http://www.patsythompsondesigns.com/free-video/
though if you have the 505 maybe you've seen it?
The truth is that FMQ is a HUGE learning curve and it takes a lot of practice. A lot. And then some more. And then if you don't do it for a while you have to kind of remember how to do it again. I make my practice pieces out of old sheets and felt or fleece (whatever scrap pieces are hanging around).
I really like the FMQ blog which other's have linked to. This piece is REALLY useful: http://freemotionquilting.blogspot.com/2011/02/loops-tension-or-speed.html
all about loops on the back and tension issues. It really depends on your machine there. I have a finicky machine when it comes to tension so I mess with that a lot. Be sure to check the bottom of your quilt sandwiches for loops.
More advice - you need the right size needle, either 14 or 16 depending on your thread. You need the right kind of thread although that's somewhat of a personal choice.
I have also found that my FMQ is better when I DO NOT drop the feed dogs. Again this is a matter of personal preference but I just put it out there because it may be worth a try.
Doodle and draw - it's helpful.
Good luck! Can't wait to see those results!