How do you ask your horse to lift his feet? If you aren't doing this already, try pinching his chestnuts, or the tendons along the back of his cannon bone. Usually either of these will cause enough discomfort to get the foot up.
As far as the lunging, when you want him to go out on a circle, stand behind his driveline (approxamately his girth line). Any "pressure" behind this point will either drive him forward or push his hindquarters away (disengagement). In this position, preparing to send him counterclockwise, raise your left hand, high, and point the direction you want him to go. You can either cluck to him or use a specific verbal cue ("walk on," etc.) If he doesn't move forward, take either the tail of your line or a lunge whip/NH stick and swing that in a smooth circle (hold the lash/string with the stick, you don't need the extra reach at this point). If he doesn't move, walk purposefully toward his hip, still swinging the stick. If he doesn't have the good sense to move before the stick hits him, fine. It won't hurt him, and he has had plenty of chances to move before this point. Continue to encourage him to move forward until he is circling you at the speed you want, then remove all pressure. He is responsible for maintaining his speed. If he starts to slow down, start asking for forward motion in the same way (Point, cluck, swing... same for in the saddle, squeeze, cluck spank... ask, suggest, encourage). Be patient, be persistent. Of course, this plan assumes that it is a training issue, not a physical issue. Be sure to rule out any pain or discomfort that could explain his reluctance to lunge.
Also, you describe him as a youngster... how young is he?? Lunging can be a good tool, but too much and too early can be really rough on growing horsey legs. Splint boots or SMB type boots are a good idea.
Hope that was helpful, good luck!