Half an hour to an hour before you go to bed, don't watch any TV.
The images stay in your head after watching it. Also, don't eat anything before you go to bed either, the digestion keeps you awake.
Try drinking Tea, unlike Coffee, it'll make you drowsy which should help you get to sleep. Warm Milk also helps.
Try going to bed the sma time every night and get into a routine.
When I have trouble sleeping, I have numerous things that I try to help me sleep.
My favourite is, if it's raining, just lie still in your bed, clear all of your thoughts and just listen to the sound of the rain. This relaxes me so much, I end up falling asleep.
Thinking of happy things that you would like to happen also helps me.
Most of the time, I just count in my head, and see how far I can count before miscounting. If I miss count, I either go back to the begining, or I just keep counting. I'm normally asleep before 100.
As for your phone, turn it off, and place it somewhere, where it's faaar away from your bed, because once you're warm and comfy you probably wont want to get out of bed again ;D
Just politley ask your sister to keep it down because you're trying to sleep.
I hope this helps somewhat. ^^
