Make sure your insurance is up to date.
Have you ever heard of 911 ? Try it ...
IF you smell smoke ; its BEST to let a professional find it , they are TRAINED to take care of it instead of waiting until the smoke catches fire and burns the house down .... Maybe tell the dispatcher that you SMELL smoke and ask their advice ... ????
check all your appliances and lights
What does the smoke smell like?
turn off some of the fuses at teh fuse box and see if you can tell what room the smell is strongest in
Are you in a single family or apartment?
It's a couple hours later now. Are you still with us??
Look at your hand I can see it from here,it is the cigaret.
Clothes. Did someone do camping? Is someone outside grilling maybe?
Double check everything
Are you sure it is not coming in from the outside? Just keep looking occasionally. Hopefully you have smoke detectors.
May the smoke from the neighbor's house.