Any monster of Level 5 or higher requires a Tribute Summon. Monsters that are Level 5 or 6 require one monster to be Tributed (called Release in OCG), while monsters of Level 7 or higher require 2 monsters to be Tributed. Some high-level monsters (such as "Moisture Creature") require 3 monsters to be Tributed in order to activate an effect.
Cards like "Mausoleum of the Emperor" can bend the rules of Tribute Summoning by allowing you to pay Life Points instead of Tributing monsters. However, this means the Summon is then considered a Normal Summon and not a Tribute Summon.
A Tribute Summon is treated exactly as Normal Summon, except a few cards refer specifically to whether or not the card was Tribute Summoned (such as Monarchs). Normally only one Normal Summon (including Tribute Summons) can be conducted in the same turn (exceptions: see "Ultimate Offering", "Double Summon" and "Chain Summoning"). This means you cannot Normal Summon or Set a low Level monster and then Tribute it immediately to Tribute Summon a high Level monster.
Tributing a monster for a Tribute Summon is a Cost. Therefore, if the Tribute Summon of the new monster is negated, the Tributed monster(s) will not return to the field.
Types of Monster Cards
Types of Spell Cards
Types of Trap Cards
ATK • DEF • Level • Attribute • Type
Playing Field Zones
Types of Summon
Types of Monster Effects
Types of Effect Monsters
Types of Spell Speed
Aqua • Beast • Beast-Warrior • Dinosaur