This is one time where having status in hotel loyalty programs help. Some will let you check in early at no extra charge. I've used this at IC and Hilton places pretty regularly. I don't know if I've checked in before 7am, though.
Some may have a reduced rate for a half day, or I always just say I have a reservation, and I understand I can't check in now, but please do what you can. Often they just let me check in then.