It's one of the more challenging forms of photography. Animals are difficult to approach, so knowledge of the animal's behaviour is needed to predict their actions. Photographing some species may require stalking skills or the use of a hide/blind for concealment.
In general, wild animals are scared of people, so you need to avoid noises or move abruptly during a photography session in nature.
Patience is most likely the number one skill you need to have for wildlife & nature photography. If you don't have patience, don't even think to start with this kind of photography.
Capturing wildlife and nature photos is not the same as a model shoot, sports event or a simple family gathering; the subjects don't follow commands or have predictable movements. Observe the surroundings and check for nice backgrounds if you're going to get really close. For birds, they have the habit of following the same route when flying around, and they usually use the same branch to rest on.
When doing a long trip or vacation abroad, I always check what to expect at the location. What kind of wildlife would I encounter, and what are their behaviours? Although I prefer to go solo, it's sometimes recommended to consult a local guide, after all, they know where to find all the best places for wildlife. Climate is also important to take into account. If you go for a trip to the cloud forests of Costa Rica or the Colombian jungle, be prepared for heavy rain showers, so dress accordingly and protect your equipment with a rain cover from LensCoat (see photo)!