Left: fox with photographers at the British Wildlife Centre.
This isn't my idea, but is one widely held amongst wildlife observers. Wherever you live, there is hopefully an area fairly close to you with a significant presence of mammals, birds, plants or whatever else you like. It may not be the obvious wildlife paradise - an area of wasteland for example - but needs to be somewhere that you can visit often, ideally at least several times a month. If it has a mix of several habitats, e.g. woodland and grassland, that is even better.
Right: One of my 'local patches' is a beech wood near the Hampshire/West Sussex border. It is seen here in autumn during light rain (hence the mistiness) but I enjoy visiting it at all times of year.
Below: Fox cub in my back garden - you can't get much more local than that!
In my opinion the 'wildlife' part of wildlife photography is more important than the 'photography' part! It is 75% about finding and watching wildlife, and only 25% about taking photographs of what you see. Otherwise you have the wrong attitude.
Right: You can't consistently get this close to truly wild animals (in this case, a male roe deer) without understanding them. Not saying I'm perfect in this respect...
Taking roe deer as an example, for a time in the spring they look very scruffy because they are shedding their winter coat. That isn't a reason not to photograph them, but it is useful to know what you are likely to see.
I suspect, like I did, most amateur wildlife photographers get their camera and then go looking for wildlife. Actually it would make more sense first to improve your ability to find and get close to animals so you can observe them without disturbing them. Once you can do that consistently, then start using your camera. You will end up with much better photographs that way.
There are dozens if not hundreds of useful books. One that I have found useful in learning about mammals is Simon King's "Wildguide" (available second-hand e.g. through abebooks). You may also find that local wildlife groups such as the Wildlife Trusts put on talks, guided walks etc. that will add to your knowledge.
Whatever camera gear you have, whether it is entry level or 'professional' quality, make sure you know how to get the best out of it. Having the most expensive gear is no guarantee of good photos... which may be some small consolation if you currently have more basic equipment!
Right: photographing a pet or other domestic animal is a good way to practice many aspects of wildlife photography.
If you were doing some kind of fairly serious athletic activity, such as running a long distance race, you would spend plenty of time practising beforehand, so that you would be at your best on the big day. Similarly it is worth practising your photography techniques before the opportunity to take an amazing photo presents itself.
Right: A wild fallow deer at Bolderwood Deer Sanctuary, New Forest. Food is put out daily, and the deer gather just yards from a crowd of screaming kids and barking dogs - whereas in any other situation, the same animals would run a mile at the slightest sight or smell of a human being - which gives you an interesting insight into deer behaviour! To me this doesn't feel like 'proper' wildlife photography, but it is an opportunity for practice.
Through practice and experimentation you will learn what is the highest ISO (sensitivity) that it is worth using on your camera before the picture quality is too poor to be worth using. Wildlife is often most regularly seen first thing in the morning and in the evening, when light levels are low. Holding your camera steady so that you get a sharp photo is an acquired skill, and it is better to practice on a boring 'target' at home first, rather than getting blurred shots in many of your early real wildlife encounters.
Today, there are dozens of wildlife and nature photography holidays and courses, lasting from half a day to a week or more. True, some can be very expensive! Some of the shorter ones run by professional wildlife photographers are good value though, and what you learn on them can significantly advance your photography. I have been on a few, with David Plummer and Andy Rouse, and also found myself inspired as well as learning new skills.
Above: On special photography courses run at wildlife centres (like the British Wildlife Centre, seen here) the keepers sometimes use food to ensure that the animal moves to a good position for the photographers. As you can see, the animals like this too!
Through courses you can also find some good photography locations, where wildlife can be regularly seen - and where you can return again in future by yourself.
Books are another good way of learning about wildlife photography. They are probably a matter of personal taste, but myself I like:
Andy Rouse, "Photographing animals in the wild" (covers UK wildlife, includes things like hides, stalking etc. - published in the film days but 90% still relevant in the digital era)
Andy Rouse, "Wildlife travel photography" (despite the title, a great overview of wildlife photography in general)
Steve and Ann Toon, "Success with wildlife photography"
These are not necessarily always the best places for wildlife photography, although they can be great locations for it. The presence of lots of other people may mean a nature reserve feels anything but 'wild'. Sometimes visitors to the reserve are kept at a distance from the animals, so you cannot get close enough for a good photograph, and there is no possibility of getting closer by stalking. At zoos and wildlife centres, it may be hard to take a photograph that does not show obvious signs of captivity such as wire fences or concrete floors.
Right: captive otter at the British Wildlife Centre. It is a challenge getting a wild-looking shot in this sort of situation - but fun, and good practice!
When you are starting out, these are definitely good places to practice. Framing your photographs so that you avoid wire etc. is good practice in composition. You will get use to judging how close you need to get to animals of different sizes in order to get a good image. You can also practice some trickier techniques such as backlit subjects or motion blur, with the chance to try again if you don't get it right first time (whereas in the wild, you may only get one chance before an animal slips away). At sites with British wildlife, you will be able to observe the animals in a way that you could not in the wild (except without extensive preparations), thus gaining knowledge of the species as well as photography practice.
Below: captive badger at the British Wildlife Centre. In the wild it would normally take at least a month of preparation before you could consistently get photographs like this. Even at the BWC, you need to be reasonably quiet or the badgers will run off underground. Plus it is hard to compose photos so that any unnatural elements are excluded (like the green wall of the badger enclosure at top left in the image below)!
One of the best ways to find wildlife to photograph is to get to know people who live or work outdoors and therefore see wildlife on a regular basis: farmers, nature reserve staff, gamekeepers, or even people who simply live in the countryside or always walk their dog through the same woods. They may be able to tell you good places to watch animals, and may even be able to give you special access to places that the public cannot always go, such as private land.
Where to start? Join your local Wildlife Trust or similar group, and volunteer at your nearest nature reserve. Be on the lookout for friends of friends who may be useful contacts. Get chatting to people you meet while outdoors (it may be worth carrying a portfolio of your best images, e.g. on your smartphone or in a small photo book, so you can show some examples of your work to anyone you meet, to demonstrate that you are serious). You never know what opportunities may arise.
Above: As a volunteer warden at the Gosport Wildgrounds nature reserve, I had the opportunity to photograph the release of water voles on the reserve in 2012. In return, the reserve is able to use my photographs to publicise their work - so everyone benefits. You can read more about this here.
The most important point is: just get outside as often as you can - you can't beat spending time in the field for getting to know more about wildlife and your local environment.