There are common habits and there are great habits, the habit that has most caught our attention has been that of a young Pomeranian named Dai. Every time Dai goes for a walk and prepares to urinate, instead of lifting his paw like the other dogs, he stands on his front legs and Urinate doing the pine!. In addition to being an artist, he demonstrates great intelligence, since by placing his upper hindquarters, the urine will impregnate areas that are higher and the next dog that sniffed its territory, will think that they are being seen with a larger dog than it really is and will be deterred from invading it.
Another habit that you have told us and that is more common, is that of go around in circles before eating, sitting, doing your needs or sleeping. In the case of a puppy, when they go around like crazy when you appear with the bowl of food, it is more related to the emotion than with something else. However, getting older is usually a way of mark your territory and protect their food. When it comes to resting, in addition to spreading its smell and making its area clear, they also go around looking for maximum comfort and even scratch the bed with the leg to release any insect or pebble so they can rest on a surface comfortable and safe. Another purely biological reason for this behavior is that you are anxious, nervous or restless. due to stress or accumulated energy, more common in city dogs.
However, the most surprising reason is that they go around making their needs, and it is Because they are sensitive to the electromagnetic field of the Earth! So in the same way that birds use this sensitivity to know where to migrate, dogs use it to orient yourself and know where the north is and where the south, being your favorite orientations to defecate, in this way, it is assumed that you will find it easier to remember and find the territory that had marked. This technique therefore does not work when the magnetic field is unstable, rainy days for example, it will take longer to decide and probably not right!
Another habit common to all dogs is that of repeatedly shake our heads when a toy is taken away. This custom, despite coming from such an adorable being, follows the ritual of "kill your hunt" once trapped and immobilized, it is the way they have to finish it off, we must not forget that dogs come from wolves!