In the last several weeks I’ve attended a few conferences, and this year I will have attended a total of seven of them. There are some basic rules of conferences that seem to get broken all the time, to their detriment.
Badges

These are the back of the badges, I'm now in the habit of hacking the back to make the whole thing better.
Don’t screw this one up. The most important part of a name tag is the person’s name. In western cultures it’s the first name, and it should be BIG and readable from at least several feet away. Don’t get too creative with the font. Affiliations are great to have in there, or alternately country/state (depending on the crowd), but these shouldn’t be so big as the name. The name of the event is the least important element of the badge. INTERACT this year managed to really mess this up, with the name of the conference and silly logos taking most of the badge, and of course turning it to portrait is an awful design decision.

These are the front of some of the badges. Look at INTERACT on the left.
Some things that are “nice to have” but really should be standard in my opinion: Double sided badges (never have it be the wrong way round), a way to identify different roles (such as presenters, exhibitors, organizers), a URL/twitter handle/QR Code (of the person’s choosing).
Programs
Programs should give you a quick overview of the conference on the first page. This should be easy to read and not create more questions than it tries to answer. Give the smallest amount of information you possibly can on this summary to still have it be useful. Again don’t get too creative, INTERACT again made some mistakes here. Look at the picture. I had dozens of people ask me when things were, and where they were located. One person literally had their program was looking at the daily overview page and had no idea how to read it, handed it to me and asked where a session was.
Electronic versions in the form of an iOS/Android app are a great idea, but obviously only make sense if the conference is of a decent size. I was at IBC (International Broadcasters Conference) and they had these beautiful large touch screen displays in portrait mode that people could come up to and touch and interact with for programs/maps/information. When people weren’t using them (most of the time) they continually had QR codes for both the iOS and Andriod apps (and I think blackberry…) just scan and get it. Built into the back of the displays and hidden in the cabinet was an open wifi router that allowed one to easily download the apps along with big prominent instructions on the screen on how to connect to it. Apps should have daily overviews, and for goodness sake, make them searchable.
Food
Food is pretty easy to mess up, and people remember and complain about it long after the conference is over. At INTERACT lunches were only provided to Student Volunteers, and everyone else had to scatter and find something. With only a few hundred people this wasn’t too bad, but I know some people didn’t like having to go out and walk a ways to get something. When I was at EGOS this summer they fed all 1500+ of us, and it was good food. I’ve been extremely impressed by most of the conferences/events I’ve attended in Denmark this year. The food is consistently good and available in sufficient quantities. Sure there was lots of fish, but there were other things too. To this American at least it felt fairly gourmet. Avoid boring sandwiches, yes I know the Dutch LOVE boring sandwiches, but not everyone does. That is a lesson learned from DESIRE’11 just last week.
When it comes time for that conference dinner/reception/gala then don’t skimp. Personally I don’t care if it’s free unlimited alcohol (I don’t drink) but I know that most people want at least a few drinks. Pacing things out is important but don’t keep people waiting too long.