Since I have started freelancing I have worked on a variety of existing projects. And a lot of them had one thing in common. They didn't have a good architecture because they were coded with a "as fast as possible" mentality. Making them difficult and sometimes almost impossible to maintain and extend.
The thing is, it would have probably been quicker to do it the right way from the start. To have a proper architecture, clear separation of concerns, tests and just clean code in general. Because it is not just about showing off progress in the first couple of weeks, it is about keeping productivity up in the medium and long term.
I am not about creating code which is seemingly impressive to look at but impossible to understand. Rather I am about creating code which is as human readable as possible. Because I always work under the presumption that I am not the only one who is going to work on it.
Another thing I am big on is transparent communication. I do not like to hide behind technical terms. In fact I tend to use as few as possible, especially when explaining something to a client. I simply belive that you can't be an expert at everything and that it is important to be able to communicate with people who are not an expert at what you are one at.