START EARLY. Selena Gomez was first on TV at age 7 on Barney. Now I know you're not 7, but that just means you have to get started NOW. If you have a dream, there is no tomorrow. Step your game up and train hard.
LISTEN IN PRACTICE. One of the main mistakes that celebrities told me they made was being impatient. Being famous like Selena Gomez or any of the other Disney celebrities may seem like it happened quickly, but like you learned in Step 1, it actually took 9 years for you to know who Selena Gomez was. There's a lot of work in the background, and it starts with practice. Your teachers know things that you don't, and just because they're not famous doesn't mean they can't help you get there. Listen to their drills and master them. Do the homework they tell you to do.
PARENTAL SUPPORT. You get parental support by giving them what they want, and then they will start to trust you. If you don't live in a large market, like LA or New York, you might have to move there. That's a big step for a parent to take, so they have to be sure you are serious. That means you might have to give up texting, Facebook, and being on your iPhone and Twitter all night, and the TV all day. Instead of watching Selena Gomez, you should be doing Steps 1 and 2 to BE like her. Once your parents see you getting good grades and practicing your acting and singing or whatever, they are much more likely to give you the financial and moral support you need.
PROVE IT ONLINE. Many Disney stars, and celebrities in general, were found online. If you sing, you should be uploading videos to Youtube. Maybe you tell your dad to get on Craigslist, find you a cameraman, and if you write a song good enough, have them shoot a music video for you. You have to think like an adult and be active, and not wait on things to come to you. If you write songs, they should be up on Youtube and your MySpace page. There are sooooo many singers with NO SONGS. How can you claim to be a singer with no songs? LOLOL. Show your work to the world and they'll respond, and if you want to get famous like Selena Gomez, you need to get started TODAY!!! ;)