2. Spare Batteries- You never know when your batteries will run out on you. Even though batteries don’t tend to run out that quickly nowadays, it is still a great idea to carry an extra battery. For instance if you were taking photos all day or for when you forget to charge the batteries the night before. So always carry a spare!
3. A UV Filter - These are thin glass filter designed to screw onto the end of your camera lenses. They filter out all the harsh UV rays of sunlight. They will allow your camera's sensors to record truer colors and details. They are the best £10 insurance policy you can provide for your camera lenses. They not only protect your lens from scratches and dust but they can save a lens or two. In fact they have already saved a lens of mine, the filter shattered instead the glass in the lens.
4.Circular Polariser Filter - Do you like shooting water scape's, sunsets or other sky/water involved scenes, if the answer if yes then a circular polariser is essential. If it is no it's still worth getting one. In appearance they are similar to UV filters but they are much darker in color, usually a darker deeper blue. Lots of dust particles in the air are constantly reflecting the sunlight. This causes your eyes (and your camera) to see the light reflected back, and not the true, deep lovely colors of the sky.
The same is true with light reflecting off of water particles. Polarisers eliminate these reflections and they allow your camera to record the true blues, greens and purples of the water and sky. Polarisers also eliminate the harsh rays reflecting back from the sand. I wrote a more detailed review of the circular polariser.
5.Tripod - Well it isn't strictly speaking a item to put in your camera bag. But it is the key weapon against the devil(camera shake). A Tripod could mean the difference between a great photo and a horrible blurry one. If you want to completely eliminate camera shake then use your cameras self-timer or purchase a cable release.
Buy one; but if you do find yourself without a tripod, you can improvise by resting your camera on something flat. Or by finding something to lean on such as a wall or a lamp post. If there is nothing at all to lean or rest on then stand with your feet shoulder-width apart and tuck your elbows into your body. These tips are not as good as using a tripod, but are better than nothing.