Trimming is the act of shortening (or extending) the start and end of your clips in the timeline. It is a crucial part of editing: the fine tuning. Editing is all about timing, and moving a cut a few frames this way or that can make all the difference.
If you’re noticing cuts in dialogue are jumping out at you then it’s probably because you’ve made the cut on a harsh syllable such as ‘k’, ‘p’ or ‘t’. Try trimming forward or backward until the cut smooths out.
The magic of editing is making the transition from one clip to the next work. If the timing is right the join should really flow. The only way to see if it is right is to try it. And if it isn't working, try again. And again.
If your program has a trim tool learn how to use it - it’s probably the most useful tool you’ll ever use.
Your first sequences will quite often be too long, by at least 25% and sometimes twice as long. Don’t worry, this is normal. It’s the editors job to tell the story as succinctly as possible, and so it’s time to sculpt the film, chipping off bits here and there to give it a better form.
However, the fact a film feels too long has more to do with the pacing than with the actual length. Watch it from beginning to end and note the second you start to lose interest. Keep watching to the end though so that you don’t lose the overall form. After you’ve made your notes, make a copy of your sequence and make the changes. Then watch again. Repeat!
As an editor, you can squeeze (and extend) time. If you need to cut down a long bit of action (someone tying their shoelaces), try cutting away to something else (like the dog watching) after the first second or two, then cut back to the end of the action (the tied laces). No one will miss the bit in the middle, or question the speed with which those laces got tied. So long as it fits with the style of the film you can radically cut the action down. For instance: a seated character stands up, exits a room, enters another room and opens a drawer. You could cut this sequence going straight from the character sitting down to opening the drawer in the other room. It’s all about the point of the cut and the overall rhythm. This might work best as a hard cut on the sound of the drawer opening, or it might help to have the sound of the drawer (or door) overlapping the shot of the seated character. The options are numerous and it’s all about trying things out and understanding rhythm.
When fine tuning an edit, zoom in on the timeline to help you adjust clips
Quite often a script uses dialogue to define a character and place information rather than have it as description. But when your script becomes a moving and talking version you quite often find that there is too much talk or information. Remember, action speaks louder than words. Don't be frightened of cutting out chunks of dialogue. Get the conversation down to the bare minimum. Use cutaways or change to a different angle on the same conversation to make it easier to cut sections out.
Remember to keep fresh. Take time out if something isn’t working. If you are the director of the film as well as the editor, then forget what you planned, take stock of what you actually have and try to make the most of it. You have to put yourself in the shoes of the first time viewer every time you’re assessing your sequence.