Unlike some people I know (and work with), I'm not big on conferences. I find them equal parts interesting and incredibly tiring, like I've had the world turned up to 11 all day.
So far this year, I've been to 3, which is 3 more than the past 5 or more years - Gather, DevOps Days and Kiwicon X. I found these interesting - especially Kiwicon - but I handled them in very different ways, and with different results.
For DevOps days, I was in Wellington for one night, and then the conference day. I didn't find it too bad, as it was just one day, with nice, bright, open rooms, and I came out of it, not refreshed, but at least not exhausted.
Kiwicon was the opposite. It was in the dark, in a large theatre building (Michael Fowler Centre) and is over 2 days. I found the first day really challenging from a "staying alert" point of view, and at the end of it, I was mentally spent. The second day wasn't much better, I just dealt with it better, and that's were a lot of the tips in here come from.
Gather is an unconference, and the topics were so varied I found it quite good - plus the rooms were light and open.
So here's my tips, if your brain works like mine does:
Don't sit, especially if it's in a dark room - find a place to stand. As soon as I sit in a dark room and someone talks to me from a stage, I fall asleep - something which University trained into me. On top of that, I stand for 8+ hours a day normally, so sitting for 8 is strange to my body. Either way, standing will keep your metabolic rate up a bit, which makes you more alert. I didn't work this out until day 2 of Kiwicon.
Work out what you are going to eat beforehand, and bring it with you. For me, food also controls my mood and awake-ness, so I'm fairly careful with it. I tend towards a decent breakfast, then protein-based snacks like salami (or cheese if I'm really organised) and nuts, plus as much water as I can get into me. Anything with a lot of sugar, and it's lights out.
Get some exercise. This could be going to the gym beforehand (I don't normally bother if I'm travelling), or just going for a walk outside during the breaks. I find this really clears my head between sessions, even if I'm in a city it's like turning the volume down for 30 mins. It's not overly social - and for a lot of people, that's the point of going - but it works for me.
If you are not feeling it, take a break. There is nothing wrong in missing a session you are not overly into, in order to be fresh and alert for one you are. Same goes for the after-conference events.
In the future, I think I'm going to avoid multi-day conferences, as I didn't get as much out of Kiwicon as I could have, due to the length. But that's going to be on a case by case basis - I've just booked Codemania + Codemania Conversations - but we'll see if I can apply my own "rules" to myself for that!