Writing letters is a good way to help you shift. You'd want to write a letter to either your DR self or someone in your DR.
You first want to start by writing a normal letter to the person you want (In your DR)
Then you want to say "Once you get this letter, send me _______" It could be roses, or birds, or a horse. It can be whatever. And once you see the 'sign' you know that they've gotten your letter. Just don't make your sign something that is nearly impossible.
After you write you letter, rip it, or burn it. Get your mind off the letter. Just like shifting, you don't want to obsess over it.
Now if you want to write a letter to the universe to help you shift, it's a bit different.
You want to start of by saying "Dear Universe.." and then you want to describe where you are right now for example "Dear Universe, I'm trying to get out of the toxicness I live in, I'm stressed out about school.." The you'd want to state your fears/doubts. I know that we are trying avoid the negative but doubts are doubts and they are valid to you. This is a way of passing your fears and doubts. The you want to tell the universe what you want "I want to shift reality's. I want to shift easily. I'll shift easily and people there will teach me how to be happy. It finds me. It's easy. It's unbelievable how easy it is. Everything's amazing there. I'm still shocked on how easy it really was.
Notice how the letter goes from 'I want" to like you already have it? Yes that's what you want!
Last you want to thank the universe, sign your letter. Then let it go. You can put it in a special box, or burn it, or throw it in a nearby waterbed.
You've handed your problem to the universe. Don't go back to the letter just completely let it go. Maybe ask for signs that you manifestation is slowly coming towards you, like a rose or something.
Hope this helped you guys!