I love keyboard shortcuts, but I must admit that while I use the heck out of them in InDesign and Photoshop, I’m not as fluent in Illustrator. Here are two handy shortcuts for selecting objects in your Adobe Illustrator document that I do use quite often.
To select all the objects on a layer in Illustrator, you can do one of two things. You can Option + Click on the layer in the layers panel, or click the tiny circle to the right of the layer name in the layers panel (as seen in the screenshot). Either way, only the objects on that layer will be selected.