Problems Starting

In the past when it doesnt start, I have changed the spark plugs and it fixed it. Which i shouldnt have to keep taking them out warming them up and cleaning them to make my car start in 0 degree weather. Is there any suggestions / types of plugs to try. I have used NGK BPr7s and Bosch Plats. Also the weird thing is when it hits these 0 degree days and i change my plugs, smoke comes from the left of my exhaust manifold. I was thinking this could be either be somehow burning rich gas that is just sitting in the engine after the car doesnt turn over or probably frost on the engine? Any insite ?