Different glues are available for different needs. Tube cements weld the plastic together in a permanent bond. Used sparingly, tube cement is very effective. Liquid cement is applied while holding the parts together. The entire seam is fused by allowing the liquid cement to run along the joint.
Crazy glues are also a possible option.
Glueing clear parts requires a steady hand or a white glue. If you have a steady hand go ahead and use cement. Otherwise, use a white glue that will dry clear but weaker. Glued parts will also need to be held in place while drying. I use rubber bands for most of my holding needs.