Dream incubation is learning to plant a seed for a specific dream topic to occur. For example, you might go to bed repeating to yourself that you'll dream about a presentation you have coming up or a vacation you just took. Those who believe in problem solving through dreams use this technique to direct their dreams to the specific topic.
While somewhat similar to lucid dreaming in that problems can be solved, dream incubation is simply focusing attention on a specific issue when going to sleep. Several studies have shown this method to be successful over a period of time. For example, in a study at Harvard Medical School, Dr. Diedre Barrett had her students focus on a problem before going to sleep and found that it was certainly possible to come up with novel solutions in dreams that are both personally satisfying and reasonable to an outside observer. In her studies, two-thirds of participants had dreams that addressed their chosen problem, while one-third actually came up with solutions in their dreams.