Experiment: There is no penalty for failing so test fire the lasers often to visualize their path. This is especially important when a level contains switches as not all switches have the same behavior.
Work Backwards: Some parts of the solution may be easier if you work backward from the solar panel instead of forward from the laser gun.
Moving and Rotating: Remember, some fixtures that are placed in the level can be moved or rotated. Pay attention to the base of the fixture or select it to see what actions are available.
Retracing: Sometimes it is useful, or even necessary, to have a laser retrace its path by having it hit a mirror straight on.
Do the Color Math: If a level includes lasers, prisms, capacitors, and/or filters it can be helpful to figure out all the colors you have to work with and compare that to the colors of all the panels. With that information you can determine what colors need to be split by prisms, removed by filters, and joined by capacitors. For example: a level containing 2 white lasers, one turquoise laser, and one blue laser has a total of 4 blue components, 3 green components, and 2 red components.
Try a Different Level: All levels are unlocked from the start so if you get stuck it may help to move on to a different one. Sometimes you will see new patterns when you return with a fresh perspective. If you really can't figure one out and are desperate to see how it's done, all the solutions can be found below.