In the Plot Phase, I reveal Summoning Season and my opponent reveals Building Season. Let's say that I win Initiative and decide to play first. I let my opponent's Plot happen first. Who reveals the location to the other player first? Me, because I am the first player or my opponent because it's his Plot. Then...who reveals first when my Plot is activated?

Controller of the effect always chooses/reveals first. First Player doesn't matter in the resolution of a single effect.

After all, think Melee: the First Player doesn't have to be involved in the resolution of Summoning Season or Building Orders at all, right?

hi!

just to be sure, even if the controller of the effect has to reveal his or her character/location first, the search is done simultaneously by both players. my opponent does't see my pick before choosing what card to get, right?

Nope. The whole thing is technically sequential. You search and reveal, then the other player searches and reveals. They will always have the benefit of knowing what you are getting before finalizing their choice.

In practice, players tend to pick up their decks and start searching at the same time. There's nothing wrong with that, and in all honesty, what you pick doesn't often have a direct impact on what your opponent picks. But if it does, they are allowed to "change their mind" and get something else - provided they didn't jump the gun and reveal their choice already.

wow, this may seem lame but that comes as shock! XD almost two years and still doing stuff wrong!