how do i keep my older fireplace from smoking into house

I really haven't run into an improperly designed fireplace and chimney, so I presume they're fine on that side. However, chimney's, fireplaces and their ash-pits need to be kept clean for everything to work as intended and safely. But, your chimney damper should be wide open for proper exhausting AND then you need to adjust your Fireplace Screen's own damper (if you have one) for proper air-intake. The Screen Damper should just be open enough so the fire burns the wood entirely to ash, but quite slowly...you don't want fast-burning "roaring" fires. If you don't have a Fireplace Screen with a Damper and Glass Doors and is either wide open or just a literal screen. Then, you're burning too large of a fire and the system wasn't meant for anything more than an ambiance or baby fire. In some homes, utility room and bathroom doors were expected (standard practice of the time) to be kept closed. If your practice is different or a door has been renovated out, then exhaust fans, furnace and water heater might be back-drafting through the chimney at times.