In a nutshell: National Express coaches with wings. Do not fly with Ryanair unless you have a credit card with at least £500 credit left - if it all goes horribly wrong you'll be left high and dry in some former USAF base 60km from the city you were intending to visit, with no support whatsoever. They don't want to know. You'll need to make your own way home, which will invariably be by the most complicated and time-consuming route.
But do not use said credit card to pay for the tickets as this will incur a £10 per person transaction fee. That's per person, not per transaction. You will need a VISA Electron card (not a normal VISA debit card, very specifically a VISA Electron card) to avoid paying any transaction fees. Don't even think about needing a wheelchair.
Read, understand and follow the Terms & Conditions like your life depends on it - and no, the cost per kilo of excess baggage isn't a typo.
Sandwiches on board are at least £3.50 Don't forget to buy a Ryanair lottery ticket - it's just like a Mecca bingo hall, right down to the bus-shelter atmosphere and the class of clientele, except you're at 30,000 feet and being flown by a guy that's been told to 'limit fuel' that the plane is carrying to cut costs.
All they are interested in is scalping passengers for every little thing they can - your '£0.99' ticket can end up costing you £120.
For tales of woe: Airline Equality
Do not be fooled by Ryanair's claims to be able to fly you to Stockholm on the cheap. It won't be cheap, and it won't be Stockholm. Here are some of the airport-city centre distances between where Ryanair will land you and where you actually wanted to go.
Brussels (Charleroi) - 46km from Brussels
Dusseldorf (Weeze) - 80km from Dusseldorf
Frankfurt (Hahn) - a jaw-dropping 120km from Frankfurt
Glasgow (Prestwick) - 46km from Glasgow
Hamburg (Lubeck) - 54km from Hamburg
Marseille - 27km from Marseille
Milan (Bergamo) - 45km from Milan
Munich (Memmingen) - 100km from Munich
Oslo (Torp) - 113km from Oslo
Oslo (Rygge) - 60km from Oslo
Paris (Beauvais) - 85km from Paris
Stockholm (Skavsta) - 100km from Stockholm
Stockholm (Vasteras) - 110km from Stockholm
And of course this is often flying from Luton or Stansted; 56km and 48km from Central London respectively.