You basically have two types of photos or videos on your iOS devices (a) photos or videos taken with the iPad, iPhone or iPod touch, copied to it via the camera connection kit, or saved from emails/websites (b) photos or videos synced from iTunes.
On iPhone, iPad, and iPod touch, you can take photos and videos or save images from applications such as Safari to your device. For these photos and videos, you may use iPhoto (if you have it), Image Capture or Photo Stream.
Connect your device to your Mac. iPhoto should automatically start into import section. You will see all of your videos and pictures. If iPhoto does not open automatically, you can navigate to your Applications folder and launch it. After you launch iPhone, click import.
Note: You may enable the feature that iPhoto launch automatically. To do this, launch Image Capture, and select iPhoto from the drop down list (see image below)
If you do not have iPhoto, then you can import photos and videos using Image Capture. Image Capture should open automatically. Choose the location where you want to import your pictures or videos and click import.
You may use Photo Stream to automatically transfer your photos. To use Photo Stream, you need to have an iCloud account. Then tap Settings > iCloud > Photo Stream and turn on Photo Stream for iOS devices or System Preferences > iCloud and select the checkbox for Photo Stream for Mac.
As we stated above, using iPhoto, Image Capture or Photo Stream, you can only import photos or videos taken with the built-in camera or captured on the device. For photos or videos that were originally synced from a computer, you will need a third-party app which can copy them off via your WiFi network. Some of the apps to transfer photos or videos are Simple Photo & Video (iTunes), Simple Share (iTunes) and Photo Transfer App.