If you are having difficulty manipulating the edges of clips during trimming, try the following:
· Verify that the clip you wish to trim is selected, and that it is the only one selected.
· Expand the Timescale until it is easier to make fine adjustments.
· Avoid expanding the Timescale too far, which makes clips appear very long. If that happens, undo until the scale is the way you want it; or reduce the scale by dragging it towards the left; or select an appropriate value from the Timescale’s context menu.