Best advice for an incoming intern?

Apart from behaving like a normal human being (friendly, respectful, eating with your knife and fork) the best you can do is make sure to remember / take note what people are teaching / telling you

Take good notes. Try to ask questions at a time where your mentor/manager doesn't seem really tied or stressed with something else. 

Be an outstanding active listener. Take great notes. Don't be so quick to ask a question as listening generally provides the answer without the question being asked. But, ask questions if you don't understand something, want to clarify, etc. But ask good questions. Ones that matter, not just to look good or stand out. That's very transparent. Be a sponge and do accurate work. Spellcheck (and grammar) is a must! Typos are lazy.