Your rights when flying to Europe

Europe (and the UK) have strong protections for flyers in the case of delayed or cancelled flights. However very few people are aware of these, and airlines will almost always try to wriggle out of paying up. Even travel agents are often unaware of these laws, or unwilling to fight the airline for you. Given the rollercoaster that flying to/from Israel has been in the last 3 years, I've had my share of experience forcing airlines to pay up what they owe, so I thought it might be valuable turning that into a post. These regulations are enshrined in EU 261.