My 300D wont lock on a point in its AF setting

That's a pretty big question, and we don't know what level of answer you're looking for, but very basically, you need to check that everything is set up correctly, and start off with the AUTO mode. So...

1. Lens fitted, and lens cap off?
2. Battery charged and fitted?
3. Memory card inserted in the slot?
... you should be ready to go.
If your lens has a switch that says AF/MF, set it to AF (autofocus). Turn the dial to the green square (auto setting).
Turn the camera on (look for "OFF" / "ON" lever).
Point at your subject and press the shutter button.

If you wanted a more specific answer, please post a more specific question.

A couple of possible reasons:
You are trying to take the shot with the lens too close to the subject. If you attempt to take a shot with AF on while too close then the camera won't take the photo. Try backing up from the subject a bit.
Which camera mode are you in? If you are using the green box (automatic) mode then in very low-light settings the camera may refuse to take the photo.
The AF on your lens might be broken. Try using a different lens (if you have one available). Do other lenses have the same problem?

Do you have the switch on the lens set to AF and also you have to go into the settings and set the focus to AF it might have accidentally got switched to MF on the lens or in the camera settings. if they both aren't set to AF then it wont work Hope this helps

The AF point will luminate very briefly when you press the shutter half way. To change the AF points press the Zoom in button + and then use the dial on the top to select the point you want. If you are not able to do this go into the Menu setting and under custom funtions go to No. 13 and set this to 0:Normal.

To get the image to focus and remain focused while you recompose set the shooting mode to 'One Shot' do this be pressing the AW-WB button them turning the top dial to get to 'One Shot'. When in 'one shot' press the button half way recompose whith out lifting your finger and squeeze all the way when you have recomposed.

Hope this helps.

Just a wild guess, but in predictive AI focus mode you need a subject in motion for focus to lock and focus adjustment is continous until the exposure is made, in one-shot AF or manual focus mode focus will lock on still subjects. Super nice camera btw.

If you are in full auto the camera is going to meter to the brightest point. If your subject is in the sun you should be ok but if your subject is shaded then they will come out dark becouse the camera is metering for the brighter background. You might try seting your camera in AV or TV mode and then set your camera to a single AF point. This will let you camera meter to just your subject and not the background. Youe could also try using a flash fill to balance out the light.

I had the same problem and I thought it was the lense. The problem was the camera focus set up. You can spot focus on one of 5 points or take an average reading of all points. If you don't have the center point set you will take out of focus photos most of the time. Read your manual about AF and how to set it. It is easy to bump the zone focus button and rotate the dial by accident. John

AF single or AF continuous can be selected. In AF single mode, focus is calculated and set when the shutter-release button is pressed partway down. This mode is mainly useful for a stationary subject. In AF continuous mode, camera continues to focus on a moving subject even when the shutter-release button is pressed partway down. It is convenient to capture the moving subject. When setting spot focus point in AF continuous mode, subject tracking can be used. (Subject tracking can be turned on/off by the recording menu. ) When selecting the Spot Focus Point, Full Time AF can be used*. * Full Time AF can be turned on/off on the setup menu. * Sensors mounted on the grip and on the eyepiece detect when the camera is held.

The DiMAGE A1 controls shutter speed in the range of 30 sec. to 1/16000 sec. in 1/3 increments. (at bulb maximum 30 sec.).

One Shot AF will focus on something and stop the AF process. One Shot AF will not fire the shutter until the lens is in focus with something. This AF mode is available in some PIC modes, like Macro mode, I think. AI Servo AF will not lock the focus, and if the subject or the camera moves, the camera will continue to seek a sharp focus. Servo AF will allow the shutter to fire whether in focus on not. This is mode only available in the Sports PIC mode. AI Focus starts out in One Shot AF, but if it detects subject movement it switches to AI Servo. It does not switch back to One Shot unless you release the shutter button and start over. This mode is available in P, Tv, Av, M and probably some PIC modes. The DRebel defaults to the AI Focus in most modes but switches very easily into Servo. Much easier than any other EOS camera I've used. In fact, too easily for most people. For example if the camera locks focus and you them move the focus manually (only on lenses with FTM), or sometimes if you zoom, or even pan the camera; all of these can force the camera to switch to Servo when you don't really want it to. The Wasia (Russian) firmware hack can force the camera to stay in One Shot, but it can't force the camera to start out in Servo.