Lost house cats usually do not go far. Look in,under, on top of all structures/trees in the near vicinity. Have a flashlight with you as his/her eyes will reflect in the dark. If you do see him/her, no sudden movements. Have some treats or his/her food with you. Also, if you can leave a door or window slightly open, he/she may come back in their own. Keep an ear to the outside after dark. Many kitties come back after dark and meow to be let back in. Leave a piece of clothing with your scent near the open space that is helpful.Have neighbors look in garages, sheds and other structures. Also if you did not see him/her get out or know for sure she/he did, check every inch of your house, she/he could be trapped or hiding somewhere. Good Luck!!