For subsequent courses, just move your guide lines up and proceed just as you set in previous layers -- using the same technique. Place your tie stones at the same intervals, use the imperfections of the level below to create a flatter surface for the next course, and don't forget to pay attention to your guide lines. Remember: If it's worth doing, it's worth doing right.
The only new element, now that you're building past the footer and first course, is that you need to be wary of building vertical holes into the wall's structure. Splits between stones on a course are called "joints," and joints that link upwards are called "runs." You don't want them -- even if you've been conscientious with your ties, they're a killer -- so make sure to follow this simple rule as you build upward:
Cover a big stone with two smaller ones on the next level, and when possible, always use larger stones to cover as many joints as possible. Follow this rule on the exterior walls, of course, but keep it in mind for the interior stones as well. A run that crosses through the middle of your wall is a bad idea -- it could pull whole sections down.