If you are serious about iPhoneography and like using all kinds of filters, you will probably want to look into getting some high quality photography apps to aid in your image capturing. But if you are a casual iphoneographer who likes to capture the occasional photo of your family and friends, you may be happy with the built-in filters offered by your iPhone or iPad camera.
The filters can be accessed by tapping on the trio of circles to the right of the shutter button. You will be able to preview the different filters and can have a lot of fun playing around with them. If you find that you prefer one filter for most of your shots in a specific mode (photo, square, panoramic), set that filter while in that mode and it will stay set to that filter every time you use that mode.
Don't worry if you forget to select your preferred filter before you take your photo though, you can also add filters retroactively when editing in Camera Roll. Just choose the filter icon from the options bar at the bottom of the screen, choose the filter you want, tap Apply in the upper right corner, and save.