Do you choose a new race, say a hobgoblin, or do you use your own body as a starting point and just add whatever abilities you want? I want to use it on my bat familiar and somehow give it normal sight. Can I do this?
Bats have normal vision, just limited (60'? 30'?).
But, you can't change your Type with Alter Self. I hesitate if it'd give you the quality of having eyes in the back of your head to stop you from being sneak attacked, allow blindsight (Heck, Poly doesn't give that), so on.
Actually, bat normal vision has a range of 10 ft. but do I need to give it new eyes, or can I just improve the eyes it already has? And you can get extra limbs, so extra eyes might not be out of the question.
Alter Self: "Your body can undergo a limited physical transformation, [...]. If the form selected has wing you can fly at a speed of 30 ft with poor maneuverability. If the form has gill you can breathe underwater." Are the possible changes listed (extra limbs, wings, gills) the only alterations possible?
No, they are only examples.
What else is possible? [I suggested Scent, Low-light vision, Darkvision or Blindsightis]
The entire sample list shown above is right out. You could, however, give yourself fins, fur, fangs, or claws, or a tail.
Before you ask:
fins: swim speed 30
claw damage 1d4
bite damage 1d4
tail slam damage 1d3 (+2 climb and balance)
Can you have more than one change in effect at the same time (like wings and gills)?
Yes.
The stuff in bold is from the Sage. To gain multiple changes, you must cast Alter Self multiple times.
IMC, I'd allow you to get extra eyes. Each pair of extra eyes grants +2 to Spot. The eyes have to be in the front of the head, however.
