Teachers TV has some episodes of Number Crew online - they're always good for introducing new concepts. "Storm and Sickness 1" deals with counting on. http://www.teachers.tv/videos/the-number-crew-storm-and-seasickness-1 If you want children to begin to add by counting on (rather than counting all the objects in 2 sets), then sometimes it can help to hide the objects in the first set. You need a box, laminated number cards, dice and counting objects. Roll a dice, take that number of counting objects and put them in the box. Stick on the matching number card (eg take 3 compare bears and blu-tack numeral 3 onto the box). Roll the dice, take that number of objects and put them next to the box. Tell the children that you are going to find out how many objects there are altogether. Tell them that you know how many objects are in the box, so you don't need to take them out to count them. Put the first number in your head (tap head or tap box) and count on, moving each of the counting objects as you say the number name. After you've repeated this a few times, children usually understand the concept of counting on, as you are still working in a very concrete way. I wouldn't move on to using a number line until they can independently solve addition problems by counting on using practical apparatus.