In my opinion, making a world is not that hard. You basically need to think of some basic things to start. What kind of land/water ratio do I want it to have? What kind of solar system does it have, as it can affect the planet's gravity and thus change the density of the things on it? is the planet inhabitable? Now that we have these basic thoughts, let us think of some intermediate thoughts. How big is the planet? How much volume and diameter is that? What kind of ecology is on the planet? (plants, fish, bugs, mammals) What kind of rocks can one find on this planet? (Iron, gold, platinum ores) Does the planet contain sentience, and if so, what is it? (Humans for Earth) What kind of biomes are found on this planet and where are they found? (Arctic near the poles) Is there a food chain of each area, and what is it? (this one can take a long time to develop in some cases.) Now that this is out of the way, let us go over what we have: We have a solar system, a planet, and a basic understanding of the planet. We now know what is on the planet for different areas and creatures on it and what they do on it. Lets now go back to sentience. What is this being? (mammal, fish, reptile, bird, fungus, etc...) how does it procreate? (Copulation, sporing, seeds, etc...) What does it consume/excrete? (Food/waste materials) Is it social, or not? (Hippo are social, Cheetah are not) If social, does it have a obvious leader, or is it between all inhabitants? Do they make structures? (Houses) or do they live off the land? Are they curious or not? Do they get in trouble because of it if so? Now, let us see some specific things. Do they adapt to their surroundings, or do they adapt their surroundings to what they want? (This is the biggest thing for humans at the moment) Do they fashion tools to aid their survival? If so, what are they out of? Are they themselves their tools? If so, how did they evolve to fit this task? Are they themselves a machine? If so, what made them? What was the process and materials used? What are their living conditions? Do they have a poor environment for survival? (Lizard in the arctic) What material is the base component of the being been made? (Important! Humans are made mainly of Carbon, and as such have specific weak points and strengths.) If made of a metal, How does the being survive? Does it use a non-rust liquid as blood? If made of flesh, do they fashion armor and weapons to aid their chances of survival? Does this entity make civilizations, and where? (England, Northern Europe area) Basic body type, Weight, Height, eyes, limbs, tails, etc... What type of vision does this thing have? Does it see heat, reflected light like humans, or something interesting? What kind of eyes would this thing have with that kind of vision? Now for some other things. Does this entity have magical, psionic, spiritual, or otherwise "unnatural" abilities? How do they work? Are they linked to anything specific? If psionic, does it have a special brain that allows for the difference? How did this develop? If magical, how does it access, manipulate, and store the mystical energies? What can be done with these energies? What types of magic are there? If spiritual powers arise, how does this entity access them? Do they pray for them, or can they use them for their own needs on their own? What can be done with this power? How did this develop? If it has unexplainable powers, what event caused said powers to appear? Was it avoidable? Now for some advanced thinking: Does this entity use commerce? Does this thing fit on the planet you made earlier? Where? What views doe this being have on slavery, abortion, murder, or genocide? Does it believe in marriage or any binding oath? How fast can this being to produce the next generation? Does this being breathe Air as we know it, or does it need a different atmosphere? What specific ores and gems can be found on this planet that is known to this entity? What are they used for? Does this thing use vehicles? What shape are they in? What is the gravity of the planet you have made? Using that, calculate the distance to it's celestial neighbors (planets if applicable and stars) What does one see when looking out to the night sky from this planet? Do you see constellations? After this, we have competent information on the planet, it's inhabitants, and what they do on the planet. Now for some questions: What kind of illnesses could an outsider expect to achieve if exposed to the viruses/bacteria on this planet? What do they do? How did the above things adapt to be as such? How did the plant/animal life adapt/evolve to be the way it is? How frequent does one experience an earthquake here? Are the tectonics stable? This information is needed in-between the basic and intermediate questions, sorry. This is just the basic layout I have thought of when making a world. Please let me know your thoughts on this, and if it helps or not. I focus more on the physical aspects of a planet. I apologize, as not everything is ordered properly, I typed it as I thought of it. Ironically, I prefer to explore a world, rather then know everything before hand. Sorry for the length and any typos.