The following are suggestions to make an experience more complete.
Depending on what your personal goals are for your bird watching experience, the items you will need can vary. There is no way around having a bird book handy at least for a begining birder. Whether you are watching them out your kitchen window as you drink your morning coffee, or taking a vacation somewhere exotic and hope to spot some winged wildlife, the bird book is an essential part of having a good experience.
For field identification, for the beginner, and ease of use, I would recommend the Audubon Society Field Guides.
More advanced books ../include the Sibley Guide to Birds. This book has more variations on feather colors which can help identify various birds at different stages of growth and location.
Even as I bird now in locations where I have been birding for nearly 2 decades, the birding book is always a part of the equipment I bring with. Too many times I have spotted a bird that I am not familiar enough with to positively identify in the field without referencing some source.
Regionally, there are many specialized books that offer more complete details for a specific area that can complete a birders collection and provide extra help in identification specifics.
Binoculars are a must have. I prefer the 10x50 power. I will occasionally bring my spotting scope along but find its hard to use compared to a simple pair of binos. The spotting scope is most usefull for stationary objects, such as nest watching.
Caution when purchacing binoculars and note whether the binoculars have tinted lenses on the ends. Most commonly, these binoculars are labled as being able to block UV light and/or are marketed for fishermen and others. While they do allow you to see into the water better than with the naked eye, the lenses shine red or orange and tend to drive birds away. I believe they see the lenses as predator eyes.
I carry a small spiral notebook with me so I can write down the date, area, types of birds and numbers I see. The spiral part allows me to hook an ink pen to the notebook itself. The notebook also gives me a place to write down dist../inctive features for cross reference at home with my more detailed books if I want to be absolutely sure I have a proper ID on the bird I am seeing.
Many local bird area hotspots will provide maps of that particular area. State parks, national forests, national parks, etc all offer maps (sometimes at a cost, sometimes for free). Many of these places have maps online that you can print out from home. I prefer to bring maps that I can write on so if I find a nest, or some other feature I want to return to, I can note its exact location on the map.
Bird Checklists are very helpful if your a relative newbie to the field, or new to an area. A good checklist will indicate what kinds of birds are common at different times of the year which will help you determine what it is you are seeing. Many state websites offer checklists online to print out, as do some of the birding hotspot areas. I would also highly recommend stopping into an areas visitor center and ask one of the people working the desk questions about what, where, last seen, questions.
A good camera is always a plus but dont be discouraged by how hard it is to get a good shot of a bird. I do not have very good luck taking bird pictures, in part because I dont own an expensive camera.
Several years ago I pieced together a device using a micro tape recorder and a listening device I bought at Toys r Us. The trick was to find a recording device that had a microphone input that was the same size as the toy listening device. There are adapters available for this but I wanted to avoid more parts to loose. I could listen to birds far across the fields and choose to record or not. It was also very cheap to put together this device compared to what a quality camera costs.