If you want to ensure that your conference participants are disgruntled then here are some useful tips:

1. Do not put any posters on the outside of the building where the registration desk is situated otherwise people might be able to find you.
2. Situate your conference in an institution which is locally notorious for being difficult to navigate (definitely do not use a hotel as the rooms would then be easy to find).
3. Make sure that your rooms are in at least three different buildings all of which are several minutes walk away from each other.
4. Do not provide posters, arrows or other navigational aids to help people find rooms.
5. Make sure that there are classes going on at the same time so that if a session overruns it will create a problem for the lecturer who is due to teach in the room.
6. Do not include lunch.  Make sure that the lunch break is slightly too short for people to find a restaurant and eat in time to arrive promptly for the afternoon session.
7. Keep the breaks very short so that if sessions overrun people do not have time to get to the break and then find the room for the next session. Why would people want to talk to each other anyway?
8. If you want to have a reception with speeches, make sure that it is in a public foyer surrounded by lecture theatres.  Ideally, students should be sitting an exam in one of the lecture halls.
9. If you want to organise an optional excursion for which people have to book and pay in advance, tell people at least twice what time to meet for the excursion but make sure that it actually leaves fifteen minutes before the stated meeting time.
10. Give people the wrong password for the wifi.
    

Luckily, the content of this conference is excellent with some exciting and inspiring presentations.

Edited to add: it seems that the problems stemmed from two sources.  Firstly, it appears that the conference chair ended up organising the event as a committee of one.  This is a very difficult situation (I’ve experienced it) in which the planning begins with a group professing enthusiasm and finishes with a single exhausted survivor making sure the the main priorities are met and allowing less important aspects to slide.  In this context, the conference chair did a very good job!  The second factor was that, for reasons unknown, the host university did not welcome the conference.  Apparently, conference volunteers put up posters and university staff took them down.  It also seems that when the date was booked the university said that it would be a reading week so there would be no students/classes.  However, there clearly were students, classes and exams.  This was the first time that I have been to a conference where I felt that the host university resented our being there but that is how it was.  As a final note, on the day we finished, the corridors and display boards were peppered with posters proudly declaiming “bienvenue” to a conference due to take place the following week.