[Tenant] need advice from landlords.

I'm about a month into a lease on an apartment I can't really afford. An opportunity has come up to move in with some friends. I've check the lease and it doesn't at all say what I should do before moving out. Wondering if landlord can give me advice on what I should be doing.

I already know I need to write a letter to my landlord. I know I need to clean this place as much as possible. I live in a slumlord can place. So there stuff just broken I can't fix. I never had an apartment give me my deposit back. So I don't think I will get it. What am I missing?