I always keep my a set of batteries in my camera and another set in the charger.  I don't usually "plan" to shoot, as in date and time.  However, when I do wake up and decide that it's a nice day and I'd like to go out and shoot, I do decide where I want to go before I leave the house.  There are a lot of nice parks and lots of wilderness around here, but I can also drive an hour and photograph tons of horses in Lexington, Kentucky (not sure if it's self-proclaimed or not, but the water tower says it's the horse capital of the country.)  Or, if I decide I'd like to shoot the city, I can just go in the other direction and be in downtown Louisville, Kentucky in about 15 minutes, either shooting random stuff along the streets, the waterfront of the Ohio River, or the Louisville skyline.  Or, if the urge hits me, I'll just throw up my makeshift (VERY makeshift lol, with pvc pipe, 2 flood lights, and 1 spotlight, and a white, black, or chromakey green backdrop) studio and shoot either my husband, or my son, or my pets, or cousins. LOL  Just whatever I feel like.  I usually pack both my digital and my film cameras, and I always have my camera phone with me.  I don't keep a camera in the car though..I'm always afraid the heat or cold will damage them.