Ok so for the record, I observed a lot of people have no idea how to make a world (that does not mean ALL people, I know many know how). I have a friend named Lukaz_Lt who is really rich and has been playing this game for a while but even he needed help building. So here are some tips:
(Note that I would not be including tips for a fishing world as that will be a separate post.)
1.) Take inspiration from existing buildings (but do not entirely copy it unless you want to).
An example of this is I want to design my world based on the Disneyland Castle. So if I were to entirely copy it, I would get blocks similar to the looks of it and build it. But a suggestion is to just use that as inspiration and make your own based off of that like, changing the blocks, adding some parts, or change the theme of the build (such as ancient, tech, nature, fantasy etc.).
2.) Base your build on a theme
For example, you want to build an ancient themed world. So you can get blocks that are similar or are ancient looking blocks (you can even add blocks that blend well and are not even ancient themed). You can search pictures that are ancient themed (applying no.1) and make your own world that way.
3.) Use colors that fit well
Using colors that fit well together such as deep purple and blue, or yellow and blue and more will make your world eye-catching. You can make an awesome looking world but it has a bad color scheme. So using colors that fit with each other as well as the actual build will show your creativity and your style.
4.) Build with a group
Building with friends is a fun way to making your world. It can take a lot of time for you on your own to build something. But if you have a group, it can speed up the process and not give you a hard time.
5.) Take advantage of the terrain generation (note: only for certain builds)
So the terrain generation is the generated world when you make a new world (everyone knows that) but if you are planning to make a certain build, using the terrain to your advantage in building something can help you. For example if you want to make an underground base, you do not need to clear the top and instead you can just dig down and make you build under there. Another example is if you are going to make a parkour that is nature based, you can just use the normal not cleared world as a part of your parkour at the same time adding new things.
So that is it, if you have any questions, reply down. If you got other suggestions, also reply so you can help other people as well. If you have any negative comments, yea, reply those down too, it actually helps me get better at what im doing so I can adjust.