Don't get sued – how you could end up in trouble without realising it.
Photography can be a tricky pursuit in many towns and cities, which probably goes some way to explaining the popularity of landscape and wildlife photography – coastlines and birds don't answer back, or take you to court, for that matter.
While a bit of care and common sense will keep most photographers out of trouble, there are some legal pitfalls to watch out for.
1) Shooting a wedding or portrait? Get insured
Public liability insurance covers you against third party claims from members of the public. Say the bride's mother tripped over your lens bag and broke her hip, or you knocked a phone out of a guest's hand while they were taking snaps, and it smashed (this happened to me!)
You would be liable for compensation, and if you couldn't pay it, court could beckon. Professional indemnity insurance for photographers is also needed if you have a problem with a client – maybe the bride doesn't feel your shots are in your advertised style, or your camera packs in and you don't have a backup, or you lose the card in the pub on the way home.
These are all perfectly possible scenarios, that could also apply to many other types of commercial photography.
2) Be careful when dealing with the police
In the UK at least, the police rarely go out of their way to pick a fight with photographers, but you need to be aware of the impact of recent anti-terrorist legislation. Police officers can stop and search anyone who they reasonably suspect to be a terrorist under Section 43 of the Terrorism Act, which means they can ask to see what's on your memory card.
They can then seize this as evidence, but interestingly, they can't force you to delete images on the spot. Section 58A of the Terrorism Act 2000 covers the “offence of eliciting, publishing or communicating information about members of the armed forces, intelligence services or police where the information is, by its very nature, designed to provide practical assistance to a person committing or preparing an act of terrorism.”
So you might get asked why you are photographing the police, or a member of the armed forces, or why you are taking pictures of a military base. Always keep calm and polite; unless you really are working for ISIS, you're usually doing nothing wrong, but you might well get into trouble for verbally assaulting a police officer or trying to run away!
For further info on US rights see 7 Rules for Taking Legal Video of Police Officers
3) Private property, harassment and obstruction
You are usually fine to take photographs of private buildings from a public area (though be careful about places of national security), but you could get nobbled for trespass if you then go into these buildings and keep shooting.
Similarly, there is nothing to stop you enjoying street photography but if you obsessively follow somebody around town all day, or keep poking a telephoto through their window, they might report you to the police for harassment.
Another convenient way for the police to 'move on' photographers is to accuse them of obstruction, so make sure your tripod or gear bag isn't blocking any public rights of way. For a fuller guide to the law and photography in the UK, see here.