If multiple effects modify your hand size, apply them in timestamp order. For example, if you are affected by Cursed Rack (an artifact that sets a player's maximum hand size to four) and then put Thought Nibbler onto the battlefield, your maximum hand size would be two. However, if those permanents entered in the opposite order, your maximum hand size would be four.
Random a card of Magic: The Gathering (MTG), but you can also roll the D20 dice, random a Planeswalker, have fun with the random rules and more.