How to tell high-quality food from the rest in a stockpile

To train exotic animals you need a dungeon master. Once you have a Dungeon Master you can tame exotic animals. Once the animal is tame you can then train it as a beast of war.

In version .31 and upwards the dungeon master has been removed. He is no longer needed to train large animals in .34, in .31 he was. But there was a bug that prevented him from showing up.

By default, bags of sand are stored in a Furniture Stockpile. But you can also mess with the stockpile settings (q, cursor over the stockpile, s) to restrict your stockpile to only sand. Under the "Furniture/Siege Ammo" category, sand types are under the "Metals" settings.

On another note: if there is exposed sand on your map you can tell your dwarves to gather sand (so you don't always have to buy it from a trader). You need to set up a zone over the sand on the ground and designate it for sand collection. Then, at a glass furnace, issue the collect sand task.