5 Top Tips for Final Cut Pro Editors

Digital Cinema Preview
Especially when you don't have a second (or third) display for playback, this is a really useful feature for watching back videos in full screen. First make sure to go to VIEW, then EXTERNAL FRAMES and click on ALL FRAMES. You might find that this is ticked already, but worth checking anyway as it's key to making this work.
Following this, whilst still in the VIEW drop-down menu, click on VIDEO PLAYBACK and select DIGITAL CINEMA DESKTOP PREVIEW – MAIN. Your canvas will then fill the entire space of the monitor, allowing you to watch your work back in all its glory.
This is also a great thing to do before delivery/completing any piece of work, because it's very easy to miss things in the canvas that become apparent once you blow it up to full screen.

Using Dissolves and Transitions Effectively
Just because you have a large amount of transitions to throw into the mix, doesn't mean you should. The best editors allow the transitions to seamlessly move the edit along without distraction, and at the points where you do see one, it's been put there for a good reason.
Noise Industries (FX Factory) do a great mix of funky transitions and effects in their plugins, but you would really only want to use these sparingly and with purpose. The last thing you want to do is pull the audience out of the experience by 'twirl' wiping the screen, or by throwing in paint splashes that do nothing but distract.
There's a good reason that simple dissolves are still so popular (and my most used transition), especially when it comes to showing a movement of time/setting in my edited piece. Whether it's a film, a corporate video or a music video, as an editor it's important to always be thinking about the purpose and target audience of the film, and reflect that in your work; in most cases, less is more!
Camera Moves & Static Shots
A really simple trick this... It's similar to the Ken Burns effect, and will help to add steady movement to a shot, that can be impossible for a cameraman to get without the right equipment.
To dolly forward/push/zoom a shot, firstly load your clip up into the VIEWER; a good example to test with might be a wide shot of a building or a room. In the MOTION tab, under BASIC MOTION, add a keyframe (by clicking on the diamond) next to SCALE. Then within the window, move to the end of the same clip and add another keyframe. Set the scale (which by default is at 100 to most clips) to 105 or 110 (depending on the length of the clip).
If done right, your shot will slowly move forwards. You can also reverse this by putting in the numbers the opposite way around, so that the shot 'pulls back' instead. A useful little trick for any form of video production, I'm sure you'll agree!
Make a Freeze Frame Still Image, and Export (optional)
In Post-Production, chances are you'll be asked to pull still images out either to use in your edit, or to export for a client. It's really quite simple, and there's a couple of ways to do it.
The first way is through Final Cut Pro of course, and this is particularly great if you want to freeze frame a shot. The first thing to do is position your playhead at the frame you would like to turn into a still; this can be done in any of the Viewer, Canvas, or Timeline. Then go to MODIFY, and then select MAKE FREEZE FRAME.
Your freeze frame will show up in the viewer window with a default duration of 10 seconds (unless you've set it otherwise). You can adjust the in and out point here, to the duration you want. For speed I typically drag the clip straight into my TIMELINE and trim from there.
With the same clip selected, you can also choose EXPORT, then USING QUICKTIME CONVERSION, and choose STILL IMAGE from the Format drop-down. This will save a still image to your computer as a JPEG for example) to use outside of FCP.
The second way, is more for those who want a still that they can use outside of the edit specifically. So for example when your client wants a few stills from their finished video. In that case I recommend purchasing DV Kitchen, which amongst other things  has a Timefreezer option where you can save a high quality still image to your hard drive, at your desired frame size. There's also a quality slider, which you can alter as per your ouput requirements.
Batch Export
A final handy tip, when you have lots of sequences/videos to export, and don't want to have to do it individually.
Highlight all the clips/sequences you need to export in your BROWSER, then right click (or CTRL+click) and choose BATCH EXPORT. Your videos will load into another window, at which point you'll want to select SETTINGS (at the foot of the window) and set the format, codec, aspect ratio as required. Once done, click EXPORT and you're away.
Worth noting that if you are exporting sequences marked with in and out points, you'll need to tick that option in the Batch Export settings.