One of the most common issues that I encounter among intermediate and sometimes even advanced guitar students is that they don't know how to achieve the most with their practising. They usually try to memorise a piece, then play it from the top a few times, and move on to the next.
This approach is not what I consider purposeful practising, as it doesn't lead to the mastery of any of the aspects of performance. This epidermal handling of repertoire hinders the chances to unlock hidden details. In other words, you ought to become an expert!
Here are the steps I take when I'm learning a new piece.