Here's how you move an accident victim. If at all possible, leave them be. Especially if you suspect head or neck injury. But sometimes, the accident scene is a very dangerous place to be. There could be a fire, or there could be oncoming traffic, so you really have to weigh your options. What is safer: moving the patient, or leaving them where they are?
If you do have to move the patient, you want to be very careful of their head and neck. Try to move them as one unit. Don't twist the head, and don't twist the shoulders. You want to grab them from this area, and then let the rest of them drag.
Head, neck, and spine - you really want to watch what you're doing with that. Move slowly, move carefully, and try to keep it all in alignment.
If you have another pair of hands, or somebody else is on the scene, help them move the person as best you can to get them out of harm's way, and to keep their head, neck, and spine stable.
You may also want to move the person to put them in the recovery position, or to get their legs up if they're in shock.
Always be mindful of their head, neck, and spine. You don't want to cause any more damage, inadvertently, when you're helping them.