Use Real-Time Preview (Windows) or Preview To Screen (Mac OS), render-scrub in the Timeline ruler while holding down the Alt key (Windows) or the Option key (Mac OS), or generate a preview of the work by pressing Enter (Windows) or Return (Mac OS).
The track selector tool sets the direction of the transition between the two clips.
Anti-aliasing smooths the edges of an effect, reducing the rough appearance of the edge. This can be useful for transitions that have angled or curved edges.
The Forward/Reverse button sets the direction of the effect used in the transition. For example, in the Zoom transition, F zooms in and R zooms out.
Select (check) Show Hidden in the Transitions palette menu, or select (check) Animate in the Transitions palette menu.