I get a mirror image

It's not possible to take a photo in a second, because the camera needs to get in focus the object you're taking picture of.

You have a square on your display that indicates where the focus will be.
With whatever function you use, you need to press the shutter button halfway and wait for the camera to focus on the object. When it's focused you will hear the click and the square will turn green.
Now your pictures shouldn't be blurry.

Panasonic Viewfinder - Mirror image:
Although I don't own a Panasonic, my Samsung and JVC camcorders have this flipped image function, so I guess most are similar in theory.
The mirror image is a function used for taking selfies, or where you want the subject to frame themselves while previewing the image on-screen.
This only affects the viewfinder screen, not the saved video or still, which remains as normal.
To correct this, you need to navigate to the 'settings' menu, exact location depending flavor of camera.
There should be an option for "self-portrait" mode or similar.
Switch this back to normal mode.
Why mirrored?
When screen is rotated 180 degrees to face subject in normal mode, they would see an inverted image, so the "selfie" function flips the graphic to compensate.
Regards,
Clive.

How do you hold your camera? Holding it at arms length and viewing the subject through the screen will practically guarantee a blurred image with most cameras. You might get away with it with cameras equipped with Image Stabilization but not compact digitals.
Use the view finder and hold camera firmly against your face. Frame your subject, take a breath in then exhale, stop breathing momentarily and squeeze the button. (Don't forget to start breathing again!) If possible rest your camera on or against a solid object while shooting.

No. It's simply a menu setting to show you where potentially overexposed highlights in the final image will be. The function can be set to show shadows or highlights.

I don't currently have a manual to hand, but if you can't find how to turn it off in your own manual then report back and I'll have a thorough rummage for one.

That is a problem that has to do with the Flash...make sure your flash settings are not turned on. If the flash can't find an image...it rotates and usually never finds the image. It's reading in a Flash mode.

What lens are you using with the D40? Is it an AF-S lens? And is the Mirror Lockup on? Chech the Custom Settings menu. If mirror lockup is on, turn it off.

Here's your answer:

This camera as with the majority of other DSLR's is UNABLE to display the image while you are trying to take it. There is a mirror in SLR's that blocks the sensor; you can only see the image through the eyepiece. This is a good thing. Using the screen on the back does not give you as clear of a picture or as an approximate image.

Some newer DSLR's like Canon's 40D/ Nikon D300 are capable of displaying the image on the screen but the camera is much slower when using this mode (it must close the mirror then re-open it before exposure happens). Its ONLY preferred when shooting on a tripod.

So to answer your question - you can't do it with your XTi. Period. Sorry. (not that, thats a bad thing though).

This is a Digital SLR With SLR cameras you can only use the viewfinder because the image comesi nto the lens and up to the viewfinder via a mirror. When to take a pic the mirror flips up[usually with a crash] and the image goes to the CCD- afterwards you will get an image briefly in the LCD.

This is becoming a common problem on the Digital Rebel. The pin that activates the sub-mirror ( for autofocus ) has broken off and the mirror box will have to be removed to replace it. It's about a $150 repair.