A good question has one defensible answer
The fastest way to lose a room is a question where two of the four options are arguably correct. Before you write the answers, make sure the right one is right beyond argument and the other three are wrong beyond argument. "Largest country by area" is clean. "Best-known composer" is a fight waiting to happen.
If you find yourself needing to specify "according to X" to make an answer defensible, that is usually a sign the question is really about X and should be reworded to say so.
Make the wrong answers plausible
The distractors — the three wrong options — are where a question is actually made. If they are obviously silly, the question is a giveaway; anyone can eliminate their way to the answer. Good distractors are things a reasonable person might believe: the almost-right date, the neighbouring country, the more famous name for a thing the less famous one actually did.
The best questions are the ones where the obvious answer is the trap. A newborn has more bones than an adult, not fewer. The letter that appears in no US state name is Q, not the X everyone guesses. Questions built this way reward people who actually know, instead of people who guess well.
Keep the question short
A question is not the place to show your research. Every extra clause is another thing to read under a timer, and quiz questions are read fast. Say the minimum needed to make the answer unambiguous and stop. "How many hearts does an octopus have?" needs no preamble about cephalopods.
Range your difficulty on purpose
A set where every question is hard is not challenging, it is discouraging — people stop guessing. A set where every question is easy is boring. Aim for a spread: a few most people will get, a few most people will miss, and a majority that reward attention. On omequiz you tag each question easy, medium or hard, and a round that mixes all three keeps a group with different strengths in the game.
Test it on one person
Before you publish a quiz, read it to one friend who has not seen it. You will find the ambiguous question, the answer that is actually wrong, and the one that is so obscure it just annoys — in about five minutes. That single read-through catches more problems than any amount of solitary editing, and it is the difference between a quiz people finish and one they abandon halfway.