What are the best practices for writing maintainable CSS?

Question

I am just starting to explore this area and wonder what are the best practices when it comes to production of clean, well-structured and maintainable CSSes.

There seems

Answer 1

Personally, I use the first method, but I also indent child selectors. For example:

.my-class {
    /* stuff here */
}

    .my-class tr {
        /* stuff here */
    }

        .my-class tr a {
            /* stuff here */
        }

Dunno about best practices though, aside from putting the opening brace on the same line as the closing one, and ending each property with a semi-colon, even if it's the last one.