• Turn deltabar on/off in Options > Options. Screenshot.
  

• Map your keys screenshot.
  Noted in post, may both keys not just 1 key.
  I'd like to try TrackIR instead of mapping keys. Another alternative, DecanClip. 
  Track Clip Pro (for TrackIR) review on youtube by iRacing member Matthew S aka KJ was interesting to watch (Oct 2015).
  Another to check out http://www.trackhat.org/
  

• Ctrl+PageUP and Ctrl+PageDown keys: scales user interface (black box) while in-car.
  Can also be set in the Options - Graphics tab. See shupop's youtube clip.
  
• 2015s4: F9 black box includes setting for virtual mirror field of view.
  
• Before editing, read all the points below.
• Activate UI edit mode: press alt-k.
  Object with blue background can be dragged with mouse.
  Exit UI edit mode & permanently save changes: press alt-k.
  
• Post 30.04.14: Some elements can only be moved if you grab the very edge of them.
  Try just clicking on the fuzzy edge of the black background.
  If a parent element steals the mouse down event, then the underlying movable frame can't receive the message.
  Some elements are affected by others.
  Eg. delta time window depends on vertical location of virtual mirror.
  If you move the virtual mirror, the delta time bar will move too.
  Move the 'parent' element before the 'child' element - per bug fix post this is going to change.
  
  APP.ini tweaks: /documents/iRacing/app.ini
• Before editing app.ini, exit any open (sim) session and save a copy of your app.ini file.
  
• By default you can only move visible elements
  Make all elements visible for UI edit mode.
  App.ini > [Graphics] forceVisibleWhenMove=1 
• Triple screen users turn off centre screen restriction:
  * App.ini > [Graphics] DriveUIFullScreen=1 allow the driving UI to span all 3 monitors.
  * App.ini > [Graphics] SessionUIFullScreen=1 allow the replay screen to span to all 3 monitors.
  
• Delta bar can be hidden update 30.04.14: now has a checkbox - screenshot.
  when using ghost car or delta time feature.
  App.ini > [SplitDeltas] deltaBarHideBar=1
• Before editing app.ini, exit any open session and save a copy of your app.ini file.
  
  To revert to the default positions:
• Delete the [UIoffsetPos] section in app.ini file.
  That will clear any custom placement.
   
  Transparency of the background:
  
• Increase the transparency of the UI in both driving and replay screens.
  Values 1.0 to less than 1.0 to increase the transparency.
  Values 1.0 to greater than 1.0 to decrease the transparency - UI may be easier to see.
  * App.ini [Graphics] SessionUITransparency=1.0
  * App.ini [Graphics] DriveUITransparency=1.0

• from 2016s4 release notes:
  
• A new driver character model has been fully implemented into all vehicles.
  
• The new driver has been shifted into a more accurate position in some vehicles than the previous driver.
• Due to the new driver model, the driver camera position in some cars to be adjusted slightly for a better perspective.
• All vehicle seat belts now change color to match driver selections.
  

• iRacing Camera Tool Documentation forum thread - download pdf attached to first post.
  (The one I saved may be outdated iRacingCameraTool.pdf)
• Camera tool key mapping screenshot also see Keyboard 
• Update 2014s3 (source: release notes)
  The driving camera can now be moved down 4" instead of just 2"
  
• A related forum thread (2014)
• FOV related post by DT - screenshot. See my FOV page for more information
• Using MCV and/or driverHeightAdj while adjusting the camera may cause a hiccup - post | screenshot
• Custom track cameras thread
  

• How to edit your driver's seat position ( with cockpit camera ):
  Update: DT explains in more detail - post | screenshot.
  
  * 'Esc' out of car
  * Select COCKPIT view in replay mode
  * Have car visible on screen
  * Open the camera tool ctrl-F12
  * Adjust the driving camera like any other camera
  * Offsets: X (fwd/back), Y (left/right), Z (up/down), P (tilt), at top of ctrl-F12 screen
  * To undo changes, load default car camera
  * To save your changes "Save car" before you leave the session
     When I save as, I use file names like "lower 30" because I have multiple seating postions  
  
  
• If you like fiddling click on the 'config' tab in the camera tool.
  That will show all the usable keyboard commands to move cameras around.
  Short version: use a,d,w,s keys with ctrl and alt (or none) to move the camera through all its motions.
  That way you can just hit the space bar and fiddle with the camera without monkeying around with the UI at all.
  
  
  CLICK ON IMAGE FOR LARGE VIEW
  
  
• SAVING YOUR ADJUSTMENTS:
  Save your seat edits before leaving the session otherwise changes will be lost.
  
  Per David T (2014s2): There are two exceptions, both the FOV and VanishY ie the [ ] & with shift keys adjustments are still stored in the app.ini. Adjusting them in or outside of the camera tool will automatically be saved. Since they are stored in the app.ini they are global across all cars. (See my FOV page for more Field Of View information).
  
  The reason for this was simple enough, iRacing already let you adjust these parameters outside of the camera tool, and there was no clean way to allow you to adjust these without setting up a fresh camera and forcing you to save it, so for now it is the way it is.
  
  
• "Moving Your Seat (Quick Tip)" youtube by "Empty Box"
  
  
  
  
• BALANCE VOLUME LEVELS BETWEEN CARS:
  As noted by Brendan in the same thread:
  * Drive a lap in the car.
  * Exit car, watch lap from cockpit view with camera tool (ctrl-F12) open.
  * Watch the db output in the mic meter and adjust the mic gain so that the peak output is whatever level you like.
  * Repeat the above steps for other cars, making sure to adjust it so that the peak db output is approx the same for each car.
  * "Save car" to save changes.
  Follow up post by DT:
  Equalizing volumes this way should only work between your car and a different model of car, but you can use it to make the in car sounds more balanced with the out of car sounds, that is the other camera views (sometimes they are way off from each other).  You can also adjust your engine volume relative to everyone else's from within the cockpit camera, if you run surround sound and tweak app.ini [audio] stereoStreamInSurroundBalance=1.0.
  Another follow up post by DT:
  Adjusting the mic in the driving camera adjusts how loud the car is (actual all cars are) when you are in the cockpit view (driving camera) for that car. Since each type of car has its own camera file you can adjust the cockpit volume for each car type in a race. But this does not affect the car sound when you are out of the car. Think of it as if each camera had a mic with a gain on it, all the cars produce a constant level of sound, but you can adjust the gain on the mic to balance out the volumes relative to other camera shots. Adjusting the stereo in surround parameter adjust the mix between stereo and surround sound sounds. In surround sound mode there is only one stereo sound being played, that is your own engine sound when you are in the car. Different cards play stereo sounds at different volumes when in surround sound mode (actually it is probably the surround sounds that change volumes) so this parameter lets you dial back your engine volume in case it is playing too loud, relative to your tires and the other cars engines.
  Another
  
  
• Deployed with known bug:
  Changing FOV while driving then editing the FOV within the camera tool can cause the FOV set while driving to be lost, reverting back to the original FOV when the session was started.
  
  

• Seat height +/- 2inch; "driverHeightAdj". Adjust to sit lower in car.
  Lowest setting would be driverHeightAdj=-0.050000 (note the "-" before 0)
  Highest setting would be driverHeightAdj=0.050000
  (2 inches equals 0.0508 metres)
• BUT David T explained (2014s2):
  driverHeightAdj is universal while the height in the camera is set on a per car basis.
  It is better to set driverHeightAdj to zero and editing the camera directly.
  (DT said he added together the motion from trackIR plus driverHeightAdj plus vertical offset from the camera).
  
  Follow up to that, DT posted:
  The driver height adjustment is added to the trackIR head position and the camera tools height (z). It is best to just pick one and use it rather than confusing yourself by messing with all of them. I left the driver height in the app.ini since several of you already use it, and in theory you could use that to make all your drivers sit 2" higher rather than adjusting each car by hand. So when you adjust the VanishY parameter (shift [ ]) I report its value on the screen (or you can read it from the camera tool). If it says 0 then the center of your screen is the center of the rendered image. If it says 50, then your eyes should be at the bottom of the screen, and if it says -50 then your eyes belong at the top (yes that seems backwards). From there you should be able to work out the right position. The default is -6% so you need to move your eyes up the screen by 6% of its total height.
  

Alexandre noted they couldn't change driver's seat positions; their fix:
in app.ini, [camtool] changed camTempEdit=1 to 0
(I've since seen you should check in-sim to ensure temporary edits are not selected in the Group tab of cam). 

Youtube link - I haven't watched it yet. (Thanks for the link Derek). 

Posted by David T. re Nurbugring (Jan 2016)
"... that track is right at the limit for number of cameras (256?). You are probably blowing past the limit when you copy and past a whole camera group like TV3 (with 30+ cameras in it, I assume). It is way down on my list to try and bump up the camera limit and/or make sure the tool gracefully handles things when you are at the limit.  Your best bet is to rearrange the existing cameras at that track and not try to add new ones, or clear out the cameras you don't want first then add some in..  "