On Cuddling Pony-kind:
Generic - most mature pony-kind are on average, 40 inches or just a bit over three feet tall. That comes up to about torso level, so we'd have to sit or kneel to put ourselves at their eye-level. This small size would also preclude an adult human from riding them around, although small children would get a kick out of it. Ponies, being equines, are muscular creatures (unless overweight). They enjoy a good brushing and grooming, as well.
Earth pony - no special considerations needed. Avoid tickling their flanks, as their hindlegs can kick rather hard.
Unicorns - Be mindful of the horn. Although somewhat blunt in most examples, it could put out an eye or bruise someone, if ran into. Do not touch the horn while it is energized, as that would ground out the horn through yourself and into the ground, resulting in something quite similiar to an electrical burn.
Pegasi - Be careful about their wings. Wing bones are very delicate, and a Pegasi can suffer a massive bleedout if one of their blood-feathers is snapped. Pegasi, as a general rule, are more aggressive than the other pony-kind, so it is inadvisable to aggravate them, no matter how docile they appear.
If small children are about, it is recommended to consult with the pony first before allowing children a chance to ride the pony. If children are going to ride a Pegasus, saftey equipent should be worn if this is to be a flying ride, up to and including a parachute, approved helmet and goggles. If the Pegasus is not going to fly while mounted, no saftey equipment is needed.
As ponies are equines, it is highly recommended to have on-hand a variety of treats for the pony to eat, including a salt-lick. They will appreciate your hospitality.