What @RichMan said. It's pretty much how I started and can confirm that it still is that way. Be dependable, stay modest, show up on time and ready and you'll soon become a regular call-up, probably even just a regular period.
Also, as long as you are able to manage expectations, don't be afraid to take games that you feel are above your level. For one thing, even if you get lit up, you'll definitely be improving, and you'll soon relaize that higher level also means better player & more backcheck. Essentially, stay square and you'll be left with the easy save most of the time. Having played 10 years of inline you probably already knew that but it's my experience and I just wanted to throw it out there in case you felt the transition "hurts" your game more than you'd like.