I am helping out taking pictures for a wedding today and I need to take pictures inside the limo. I have a Canon Rebel Xs and I do a lot of outdoor shooting with natural sunlight but I don't have much experience with indoor, low-light settings. What would be the best settings to use for taking pictures in the limo? I'll just be using the standard lens that came with the camera.
The biggest issue with low-light photography is (fairly obviously) the lack of light reaching the sensor causing underexposure (Sometimes combined with the shutter speed being set too low to try and compensate, and the photos suffering from motion-blur).
In terms of camera settings you're going to want to shoot with the aperture as wide as it'll go, although the kit lens isn't particularly fast, so I imagine that this won't be enough. Make sure the shutter speed isn't too fast, but make sure you don't suffer from motion-blur or show camera-shake. I'm not sure how well the latest xxxD/Rebel series cameras deal with medium-high ISO, but I'd increase the ISO a little, but you risk lots of noise if you increase it too much. They're the three things you can control on the camera.
To maximise the amount of light on the subject, I'd personally prefer to work as much with natural light before introducing artificial lights and flashes, using things such as reflectors. If there's really not enough natural light that can be directed at the subject, then you're going to have to use artificial sources, but try and avoid harsh shadows by softening the light by bouncing off the ceiling or off or through an umbrella.
The best option is to use external off-camera flash, but I assume from you question that you don't have the equipment.
So first try to push the ISO up as high as you are comfortable with and if this isn't enough (it probably won't be) just use your camera's flash - the light will be horrible but it's better than not having pictures at all.
Just remember the light will be bad, so try to capture exciting, funny or touching moments, don't try to take portraits with your camera's built in flash.
Update: normally I would not recommend the camera's built in flash but we have: 1. low light 2. slow lens 3. no external flash 4. bad high ISO performance 5. no long exposure (because we are in a moving, shaking, car) so there really isn't another viable alternative (except to seriously underexpose and hope you can recover something in post, but I think this is even worse than the popup flash)