We run these sorts of events at my firm. In general, you go straight from a day of interviewing out to dinner, so dress code isn't so much of a problem -- you wear whatever you were wearing for the day. Bear in mind that your hosts will almost certainly be coming straight from the office and/or a client, so will probably be wearing a suit. You won't go wrong wearing a suit, too.In terms of alcohol -- if it's offered, feel free to indulge in a glass or two, but don't get drunk. If you don't want a glass, no one will mind -- everyone (including your hosts) realises that these are tricky situations and that there's no one right way of handling it.In general, these sessions are unassessed -- but don't let your guard down. I'm normally asked for high-level feedback (eg, "they seemed like a nice bunch") but if you get drunk and make an ar$e of yourself, you can be sure that will get back to the HR panel as well.The evening is really designed to let you relax a little and ask the questions you aren't totally comfortable asking in a formal interview setting, about the type of work we do, the consulting lifestyle, etc ... as well as to hear some war stories from those who are actually out there delivering work for us.