Check... always check.
Check appliances, switches, bins, ashtrays (in case you use them), the kitchen, washing machine, alrmclocks etc etc.
Check each room.
In case you discover a fire, first think.
Some fires only need water, others should be treated with foam, or even sand.
Know how to deal with burning pans, a burning couch.
Never try to extinguish a fire which is not extinguished within moments.
Because the smoke is nasty, you'd better call the firebrigade and leave the building after you have warned everyone inside...if that's still possible.
Realise that smoke a disabling.
You should have a plan to leave your house before any fire starts, and you should practice it with family and friends.