Forum:What activates first?

How do you know when something activates first if it is at the same time? For Exemples: This are just some examples of things that happen at the same time, but maybe if I know theses, I maybe know the others
 * You tribute E-hero absolute zero for Caius
 * You activate dark hole when both players have dandylion. Which Dandy effect works first?
 * 2 Mystic tomatoes attack each other. Who summons first?