Folkestone is well connected to the rest of the UK as well as mainland Europe. This page has some information to help you make travel plans. This is for big picture information and hints - ultimately you should check with specific travel providers before committing to plans.
There's not too much in it between any of London's major airports, Heathrow, Gatwick, Stansted, Luton and City. Given a choice I would recommend favouring Gatwick, as it gives you more options.
From any of these airports you can get a train into London (there's a usually an express option, with fewer, if any, stops). Then make your way across London, if necessary (by London Underground, Bus, Taxi etc - Underground usually recommended), to St. Pancras (STP). From there you can take the high-speed link (HS-1) direct to Folkestone Central (FKC) in just under an hour (usually 53 minutes). If you're flying to City Airport you'd go via Stratford International (SFA) (then possibly changing at Ashford International (AFK), instead of St. Pancras.
If you are flying in to Gatwick you could take the above approach, but you also have the option of taking "slow" trains down to Folkestone Central without going through London. It will usually take slightly longer, but if you prefer to avoid London it's a good option. It's also cheaper. You will still have to change - twice (at Redhill (RDH) and at Tonbridge (TON), usually) but these are much lower stress connections than in London. A third alternative, taking a similar time, is a train from Gatwick to London Bridge (LBG), then direct from there to Folkestone.
To explore the options available at your travel times please use the National Rail Enquiries website. You might also want to try BritRail for cheaper fares.
So, in summary, these are the recommended routes:
If you're coming from mainland Europe and you're accessible to a Eurostar train service this can be a good option. The closest Eurostar stop to Folkestone is Ashford International (AFK - not the one in Surrey!). From there it's usually about 15 minutes by domestic train to Folkestone Central (FKC). Not all Eurostar trains stop at Ashford, so you may find you have to go all the way into London St. Pancras (STP) - from where you can get the high-speed line back out (usually 53 minutes). Prefer the Ashford stop if you can.
For Eurostar times and routes see their site.
For domestic trains see the National Rail Enquiries website.
You might also want to try BritRail for cheaper fares.
If you're driving in the best option is to take the Eurotunnel/ Le Shuttle from Calais, which takes 35 minutes and comes out at Folkestone (actually just off the M20 slightly north of Folkestone itself - about a 10-15 minute drive back in to the venue). Please note: you can't use the Eurotunnel as a foot passenger.
Alternatively there are several ferry routes. These may be cheaper, but take longer - and may be subject to weather conditions. Most of these also go from Calais, but arrive in Dover - about 30 minutes drive to the venue. You can also use the Ferries as a foot passenger - in which case you can take a train from Dover Priory (DVP) to Folkestone West (FKW) - which is then 30 minutes walk (or a taxi ride) from the venue.
Most of the hotels will have a small amount of on- or off-road parking - check with them before making your plans. There is also a larger public car-park immediately opposite the venue.
The nearest station is Folkestone Central (FKC). If you're travelling any distance you'll most likely need to go into London - in which case the high speed line from St. Pancras (STP) is probably a good option - especially if you're coming from the north. If you're coming in from the south then going via London Bridge (LBG) or Redhill (RDH) and Tonbridge (TON) may be a good alternative (see advice in the flights section). In any case check with National Rail Enquiries.
Folkestone is just off the M20 and the venue can easily be found with most sat navs.
Most of the hotels will have a small amount of on- or off-road parking - check with them before making your plans. There is also a larger public car-park immediately opposite the venue.