I'm now a regular game demonstrator at Essen SPIEL shows. Here's my advice in case you're contemplating it.

Choosing a Company

If you are a natural salesman then it won't matter what you demonstrate. But many people aren't, and for us it's important to pick a company that publishes games we like. Then you can just use your own enthusiasm for the product as part of the demo process; that works better on me than the world's best sales pitch, and at least some of your potential customers will be like me.

If you have a specific company in mind, it's worth writing to them before the show and finding out who's organising their demo people. They may not actually do this until the last month or so before they show. Otherwise, haunt the Essen forums on boardgamegeek and you'll find help-wanted posts.

Generally speaking, the larger the company, the more time they'll want you to commit and the more formal they'll be about break times and so on, but also the more they'll pay you.

This won't pay your hotel bill, but it should get you an entry ticket and it may pay for some of your game shopping. (If you're on a severe budget, be aware that some companies organise room-shares for their demo people, but it helps if you already have a working relationship with them.)

Scheduling

If you aren't a naturally punctual sort of person, don't even bother. Your fellow demonstrators are relying on you to turn up when you said you would.

Working all day every day is entirely doable, but it's nice to take some time off to see the show. I tend to want to be out in the show on the Thursday, to get things that will sell out quickly, and on the Sunday, to get any last-minute bargains. (Some people like to take a long time at the booths and play lots of demo games; I'm more prone to set up a list of games to try before the show, and make relatively quick decisions about whether to buy them. I'm getting better at this.)

Sunday and especially Saturday are much busier than the first two days, so your volunteering will typically be more welcome then.

The Games

Quite often, when you explain something in English, one of the group who said "English is no problem" will translate for his friend who isn't quite as good at it. He's usually pretty accurate though. Just give him time.

Obviously, know the games inside-out. Especially if you haven't demoed them before, pick up on what people get wrong and include it in the talk next time. You may find you end up with a script you can repeat in your sleep; that's not a bad thing.

If the company you're working for doesn't have a policy about demonstrators playing in games they're showing off, and most of them don't, consider what will work best for the specific game. For One Night Revolution (3-10 players) I'll always join in if I have three or four, because the game's noticeably better with an extra player, but if I have five or more players I'll usually leave them to it so that they can have the discussion phase on their own. A group that regularly plays together will probably enjoy the game more if they can get an idea of how it'll work with their own dynamic, without having to accommodate a stranger.

You may have heard the word "Kriegsspiel" if you ever played chess. Apparently it has unfortunate connotations in Germany these days; when talking about wargames, "Strategiespiel" is preferred.

Self-maintenance

It's not unusual for me to get through about two or three litres of water per nine-hour work day; it's not too terribly hot, being in Germany in October, but it's usually a pretty sweaty place. Don't forget extra salt in your packed lunch. You can buy food at the Messe, but it's expensive and not terribly filling (well, except for the big spiral of fried potato).

The maximum recommended dose for Strepsils is around one per two hours. Do it before your throat starts to hurt. You'll be talking loudly to overcome background noise. (Fisherman's Friends are also good.)

Try to vary posture between sitting and standing. Padded shoes are your friend, for hard concrete floors. I like Crocs.

Hotel

Everyone has their favourite hotel for Essen. I've used four and not had a bad one. They're all expensive, especially if you're within walking distance of the Messe. The Bredeney has the best breakfasts of anywhere I've been. Staying at one of the surrounding towns and driving in can work, but if you don't have a booked parking spot you should aim to be there early, especially on Saturday.

Travel

Bicycle facilities aren't marvellous (particularly the bumpy and unlit Norbertstraße shared pavement between the Bredeney and the Messe) but cycling is still far quicker than walking. Pity that hotel is uphill though.

You used to get free use of Essen public transport (surface, not U-Bahn) with your ticket, but not any more.

You may be able to book one of the privileged car parking spots under the Messe; talk to the company you're working for.

General

Always know where the nearest toilets to the booth are, for both sexes; apart from the obvious reason, people will ask you, because there aren't many of them and they aren't well-signposted.