Czechia is part of Schengen. Information about visas can be found on WikiTravel and authoritatively on pages of Ministry of Foreign Affairs. The organizers can provide letters of invitation for registered attendees.
Vaclav Havel International Airport Prague (PRG) has direct flights from all major airports. From some locations, low-cost flights are more convenient, but are often not supported by search engines. For all possibilities, see this list of airliners and destinations. The airport has two terminals: T1 is for non-Schengen countries (e.g. UK, Ireland) and T2 for Schengen countries. The terminals are walking distance from each other and both are served by taxis, the airport shuttle, and public transportation.
Public transportation to the Orea Hotel Pyramida: take bus 191 to the stop Vypich and then continue by tram 22 (direction to Nadrazi Hostivar) to the stop Malovanka (the hotel will be on the left-hand side).
Prague Main Railway Station is located in the city center. The stop is “Hlavni nadrazi”. The Station serves most international trains. Connections can be found here or here. Deutsche Bahn offer direct bus connections from some cities to Prague, and these are sometimes faster than trains. Note that the surroundings outside of the Main Railway Station is not pleasant and locals always try to get quickly to and from the station.
Public transportation to the Orea Hotel Pyramida: take the subway (red line C is directly under the station) to station Vltavska (direction Letnany) and then continue by tram 25 (direction Vypich or Bila Hora) to Malovanka (the hotel will be on the right-hand side).
Florenc Bus Terminal sometimes also called “UAN Florenc” or “Ustredni Autobusove Nadrazi Praha - Florenc” serves many international bus connections. Other bus terminals are also well served by public transportation. From several places in Austria and Germany, bus connections are more convenient, faster, and much cheaper than getting to an airport and flying. When travelling on budget, a bus may be an option from more distant places as well. Bus connections can be found here (click on the British flag to switch to English). Some buses are very comfortable with personal video system, refreshments, indeed toilet and air conditioning, but it varies a lot depending on the line/carrier.
Public transportation to the Orea Hotel Pyramida: take the subway (red line C is directly under the terminal) to station Vltavska (direction Letnany) and then continue by tram 25 (direction Vypich or Bila Hora) to Malovanka (the hotel will be on the right-hand side).
Googlemaps seem to be working well finding public transport stops and schedules, but once you know the names of the stops, you may check with a local connection finder for the case there were detours/construction works. There is an app called Jizdni rady for finding timetables for Android and Apple. The fares structure is complicated, the cheapest solution for participants is individual tickets (32CZK for a 90 minute ticket). 90 minutes is enough for any meaningful travel in Prague. You need to buy a ticket before entering the controlled area of a subway station or before entering a bus/tram; you need to time-stamp the ticket when entering the subway station or immediately after entering a bus/tram. Tickets can be bought in information centers. It might be easiest buying some tickets at the airport or railway station in advance. Tickets are sold in any subway station from an automated machine with coins. Ticket inspections are strict and frequent - and, unfortunately, not all inspectors speak English (so when someone stops you holding a badge and asks for “jizdni doklad”, he wants to see your ticket).
Generally Prague is safe but there are several well known risks to travellers. Pick-pocketing is common in the city centre on the streets, in shops, in public transport, close to ATMs or exchange offices - organized groups target mostly tourists; the highest risk is in crowded areas and sometimes the crowds are created artificially by well organized criminals. Simply keep your wallet well hidden and under control. Incorrectly returned change is common when paying in cache, particularly at smaller places in the street but it can even happen in large shops and restaurants - always check your change immediately (these are the coins and banknotes). Don’t pay with high denominations in the streets and don’t get distracted during the transaction. Nobody really uses the highest denomination banknotes of 5000CZK (about 185€). 2000 CZK is ok if you’re paying in a large shop and are careful when getting change (some people apologize for using such a large banknote, to be polite). A very high risk of significant ripoff exists in currency exchange offices. It is not just that their exchange rate may not be a bargain, but they often mislead about what their rate is and refuse to abort the transaction once the customer gets the money. One alternative is to use an ATM.
The local currency is Czech crown (CZK).
The mains voltage is 230V (all of European Union) and the socket type is E (like France, Belgium - should be compatible with plugs for continental Europe). You definitely need an adapter if you travel from the UK or US.
The general emergency number is 112 (all of Europe). The operators speak English. In case of an accident you’ll always be treated in a hospital no matter whether insured or not (but indeed will have to pay if not insured or not insured sufficiently). Doctors almost always speak English and often German, nurses and other hospital personnel may not.
Everyone is required by law to carry an ID card at all times (a passport or an official ID card of an EU country) and the police may ask anyone for their ID card at their own discretion (though that practically never happens). Similarly the police can stop any car at their own discretion. Drugs are illegal, except for alcohol and cigarettes.