Need to select multiple keyframes? Here are a few tips to make it easier.
Select all keyframes associated with a property by clicking on that property's name in the timeline.
Add to that selection by Shift+Clicking on additional properties.
Lasso visible keyframes in the Timeline window.
Select all visible keyframes by pressing Cmd+Option+A (Ctrl+Alt+A).
In 6.5 you can also deselect keyframes (while still leaving the layer highlighted. Press Cmd+Option+Shift+A (Ctrl+Alt+Shift+A) to deselect only keyframes and groups.