Did 6 open days with DD1 last year & gearing up for it with DD2 this year. Very helpful in separating out unis that on paper all appealed.
First impressions were important - plenty of very visible student ambassadors who were friendly and well-informed, and a well-organised day, set the tone.
City/location determined which DD even considered visiting - needed to be accessible by rail, and uni location in the centre was a plus. No preconceived ideas about campus vs city unis but visits resulted in a preference for campus. Transport for students from nights out etc was a factor. Some unis well located in that respect and had schemes to ensure students could get a taxi with student card and no cash if they needed to. Worst was a uni 20 minutes bus ride from city centre but no buses into campus Friday to Sunday!
Subject/departmental talks were key. Such a shame that at one uni two very similar courses, which DD wanted to choose between, held talks at the same time - these were at different times everywhere else. Please don't overlap similar course talks! DD was really put off by dumbing down (an apology about 'long words'), an incredibly boring lecturer at one place and poor slides at another. A comment by a lecturer to the effect that "we don't really want to cover mental health [in course content] but we have to" immediately ruled out that uni! Conversely, DD was impressed by lecturers who were professional in the way they presented themselves and their courses, didn't patronise and were enthusiastic. Plenty of information about course content and a chance to speak to current students was really helpful. But don't show slides showing the details of the course and just read that out!
DD was also keen to go somewhere with plenty of opportunities for work-based placements - this is pretty variable on her course between unis.
It was useful to see accommodation, as she had no idea what that would be like, and has moved from her starting point of "the cheapest will be fine" to "I'd like an ensuite room and to share a kitchen/social area with a small number of students".
This doesn't help you at all but aside from all these kind of things that could be ranked on paper, how DD felt about each place, from the moment of arrival (actually before with what's now her top choice - at our local railway station heading off to the open day she an advert for it with a quote she could really identify with!), was really influential. A gut reaction.
Great that you're asking and I will be interested to read the rest of the thread (when I've finished writing the article I'm putting off finishing!)