When you first set out to create a problem, whether it be your first or one of many, keep some of the following things in mind. These tips have served me very well and I wish the same for you:
Imagine how people will respond before you post it. Think of how people will respond if you change certain parts.
Appearance is key. Putting a picture in yours will make it more attractive to others. Make sure you use pretty LaTeX.
Try to make it multi-step. Take a look at the difference between the following problems:
Problem 1: What is the hypotenuse of a triangle with legs 3 and 4?
Problem 2: Find the sum of the length and width of a rectangle with area 12 and diagonal of length 5.
Notice that these problems are both based on the Pythagorean theorem, but it is obvious that the second one is much more satisfying and interesting.
Be inspired by other's problems. That doesn't mean just bluntly copying and pasting them as your own. Whenever you see a good problem, think about what makes it cool, and what makes it tick.
Math class is a great time to think of problems. Take one of those boring questions your teacher gives you and turn it into something wonderful!
Let your problems sit for a while before you publish them. There's nothing worse than a half-baked problem. Let your friends have a whack at it, and listen to their feedback.
Be clear, concise, and keep Shakespeare's quote in mind: "Brevity is the soul of whit". Wording can be the most difficult part of creating a problem.
I hope all of these suggestions and tips help! If you have others, or would like to ask questions, comment below! :D