What are those Poll Clerks doing? What do all the numbers mean? What happens to them? Why do you not have pens (#PenIsBest and #UsePen being popular on the day)?
A good starting place for anyone looking into this side of things is the Handbook for polling station staff (pdf) from the Electoral Commission. This is given (as far as I know) to every member of polling station staff. It covers everything from roles and responsibilities of polling staff to how to set up a polling station right the way through to how to transport things back to the count at the end of the day.
The main question I was asked about was what does the number on my poll card mean? Can it be used to track my vote?
The answer to this is a little complex, but simply put: Yes, it could technically be used to track your vote. In reality, it would be a huge amount of work to do so.
Most of us are used to what a poll card looks like. Below is a nicely annotated example one from Horsham Council: