Spaghetti/fat code is probably the biggest problem for new programmers - though they're probably not aware of it. It's very, very hard to make any module larger

Spaghetti/fat code is probably the biggest problem for new programmers - though they're probably not aware of it. It's very, very hard to make any module larger than ~500 lines without overcoming it. This was a huge issue for me for probably about two years. Then, I took a look at my projects using a dependency visualization tool (Structure101 for Java/C#) and I got a lot better as I fixed all of the tangled code/fat classes.