Hi,
I have really bad posture... I don't have scoliosis or anything, I just slouch a lot. I slouch when I sit, drive, eat, stand, walk, everything. I can stand up straight, but it makes my back tired... so I don't. Plus, I have to sit in a hard desk all day at school, and it feels so much better to slouch down in it than to sit up straight as a pencil.
What are some ways/exercises/habits that I can do so I can stop slouching and start standing up straight?

Thanks!