Teach your dog to close the door or turn on a light:
These tricks are taught with targeting. Teach your dog to touch your hand with her muzzle first. Present your open hand about 10 cm away from your dog’s muzzle. It is better to start with the hand to the side and not right in front of her face. Most dogs will touch if not remove your hand and try again. Once she touches your hand, say yes (or click) and reward. If she does not touch, smear a little bit of your treat on your hand.
Once you get a reliable touch, stick a post-it note on your hand and ask your dog to touch the post-it note, mark and reward.
Once that is reliable, slide the post-it note down, this way your dog is going to only touch the post-it note and not your hand. Mark and reward.
If she does this reliably transfer the post-it not to your target (door or switch).
You can teach a foot target the same way.