[RPG] Minor Effects for Magical Items

Example 1 contains the correct reading of this rule.

As pointed out by Ernir, the Magic Item Compendium contains updated rules and clarifications for the creation of magic items.

Page number 233 of the Magic Item Compendium covers this case and states that:

In most cases, if the item is one that occupies a body slot, the cost of adding any additional ability to that item is 1-1/2 times the value of the added power (or the value of the added power plus 1/2 the value of the existing item, if the added power normally costs more than the existing item). For example, if a character adds the power to confer feather fall to her ring of jumping, the cost of adding this ability is 3,300 gp, the same as for creating a ring of feather falling × 1-1/2. On the other hand, if she were adding the power of a ring of force shield to that ring of jumping, the cost of adding the ability would be 9,750 gp (8,500 gp for the ring of force shield plus half of 2,500 gp, the price of a ring of jumping).

It is also worth noting that the Magic Item Compendium updates the cost of Multiple Different Abilities to be 1.5x instead of 2x.

Rules for Identifying items are found in the DMG, though they can also be found in the basic rules, which I will be referencing here. The basic rules are free to use and can be a good substitute until you can buy your own DMG:

Dungeon Master's Basic rules, pg. 58 (Emphasis mine)

A magic item’s description explains how the item works. Handling a magic item is enough to give a character a sense that something is extraordinary about the item. The identify spell is the fastest way to reveal an item’s properties. Alternatively, a character can focus on one magic item during a short rest, while being in physical contact with the item. At the end of the rest, the character learns the item’s properties, as well as how to use them. Potions are an exception; a little taste is enough to tell the taster what the potion does.

So, you can just taste potions to identify them. For all other items, you learn what they do immediately upon casting the identify spell, or you can spend a short rest identifying the item. The tasting is not drinking the whole potion down without knowing its effect. It's just a small sample, maybe a few drops or a small sip in quantity.

Flavor, such as what kind of experimentation you do to discover the properties, or how the properties manifest themselves to the characters, is up to DM discretion. Playstyles can vary from just telling the party what the items do after the identification, to giving the players clues and having them figure it out themselves.