Why does my fireplace smoke up the house so bad?

Dumb question but are you sure the flue is open all the way?

I don't have a fireplace anymore but the few people I know that burn one and it doesn't smell like a smokehouse start with a small fire to heat the flue and chimney before they try to heat the house. My house always smelled like woodsmoke even when I had an insert.

Has it happened from day one? If so your stack might not be sized right. I have one that the guy before me diyed in my older home. I have to heat it first with a starter log for a while before I put wood on. I also must use “designer logs”. Thin, bark free, dry wood to keep the smoke down...it’s a pain in the arse

When i first light mine when the wind is blowing there will sometimes be a little smoke that comes into the house until the fire get rolling good.

I had to add another section of stack to my chimney. Was too close to roofline. Fixed my issue.

Birds or squirrels may have built a nest in the flue. Had this happen to me. Got a flue cap installed that's bird and squirrel proof or is your flue wide open at the top?

Can someone tell me what thus little lever does/is? I haven't messed with it ever but wondering it's purpose.