Depends on the specific situation. For general all-around building, liquid glue (I use Plastrtuct Bondene). Clamp the parts to be glued together, and "paint" the seam with liquid cement. It flows into the seam and "welds" the parts together. No messy "squeeze out" or "strings" like you get with tube glue. For certain other situations, like where parts fit is sloppy or I need to fill the area with something solid...5-minute epoxy. Tube glue if I am gluing a small part in place that needs to be held in position as it dries. Example: side view mirrors. A tiny dab of tube glue on the glue surface of the mirror, than place the mirror in position. The tube glue is thick enough to hold a small part like that in position as it dries, liquid cement wouldn't work well in this instance. CA glue in certain situations, or if bonding dissimilar materials (brass to plastic, wood to plastic, etc.) For windows that fit well, small trim pieces, chrome emblems, anything that needs to be placed on a flat, smooth, usually painted surface: clear acrylic. I use "Future" clear acrylic (it's actually meant to be used on tile or hardwood floors). One bottle of the stuff will last forever. Those are what I use: Liquid cement for 90% of building, epoxy, tube glue, or CA in certain specific situations, and clear acrylic.