MintshadeSo, I'm trying to improve my building - I'm doing a sort of medieval/magical theme for most of what I build - and I was wondering if anyone had any general tips? I've already gotten a few things from my friend, who just shouts "DEPPPPTTTTHHHHHHH" and then replaces my wall with an intricate collage of stairs, slabs, yadda yadda, but I was wondering if anyone else on here has some advice on proportions/detailing/etc etc etc.

Thanks!

~Mint

Never use too many stairs. Depth is important, but it can become way too over-done. Really it depends on the style, but don't take "depth" too seriously. there's a point where depth makes everything look extremely ugly.
Edit: Odd numbers tend to be more appealing to the eye. Too much pattern looks ugly, I know this from my unfinished palace that relies too heavily on pattern.

Ok, so there are 2 main aspects of creating a building. The first is the design, meaning the shape, size, and proportion of the build. The second is style, which is multiple things. For the most part, it is the time and place the building is modeled after, or era. This influences the buildings structure, details, and can often also affect the design.

If you are going to build something, have a style and design in mind beforehand. For example, a style might be "medeival" and you may have a design plan in mind for it. If you do not have a design plan in mind, you can create one. Do some online research, find other minecraft builds that suit the style you wish to build in, and see if they inspire a specific design, layout, or idea that you may want to expand on in your own build.

When designing, it is important to create an interesting layout, so not just a rectangle. Even a number of rectangles put together is a better floor layout than just one.

Also, keep proportion in mind. In medeival times, most buildings did not have high ceilings inside so keep floors about 3 blocks high, unless you are making a specifically large or spacious building, like a tavern or castle.

Now, for style. Your friend was right when he said depth is important, but there is more to it than that. Look on the internet for pictures of the dtyle you wish to do, and try to get an idea of main aspects of the style. Even if pictures of real-life builds do not have much depth, try to create or exaggerate depth in your builds to make it look more detailed. Dont overdo it though!

Also, when creating designs have an idea of symmetry in mind. Distinguishing when symmetry is and is not necessary is a skill that can be obtained through skill and practice. Rule of thumb is if a wall is adjacent to 2 outside corners, it requires symmetry. If it is adjacent to an outside and an inside corner, it doesn't necessarily need symmetry in its individual design. The assortment of design aspects (windows, supports, etc) when arranged symmetrically over the center of the wall face creates such symmetry.

Anyway, I hope this helps! It would be cool if I could see some of your future builds.
Good luck!

DEPPPPTTTTHHHHHHH!
But seriously, depth is very important in building. Use lots of stairs and make sure your walls are always 2-3 blocks deep. It will make your house look a lot better. Make sure that it has a pattern though, because otherwise it will look really messy.
Also, use lots of different types of material like wood planks, logs, bricks, etc.