Dream Incubation means in the broadest sense influencing your dream content with actions done in waking life.
Nowadays dream incubation resembles the 'enkoimesis', the sacred temple sleep which was practiced in ancient Greece. A person who was searching for advice or healing spent a night in a god's temple to get a piece of advice for his life or a certain remedy for his disease from his dreams.
But one doesn't have to travel to Greece and sleep in temples. Incubating certain dreams works well in your home too.
The topics of dream incubation are more wide-ranging nowadays. Some dreamers choose to incubate a hedonistic dream whereas other dreamers prefer dreams which lead to spiritual or psychological insights.
Whatever you want: you may ask your dream for advice about everything you want: Love and relationships, personal growth, career, even where to spend your next vacation... anything.
Or just entertaining purposes or to induce lucid dreams.
1. The easiest way to induce a dream about a certain topic is auto suggestion. When going to bed you set your intention to dream about the topic you have chosen. This method can be combined with visualization and the WBTB technique.
2. The dream incubation routine by Michael Patrick Kepe:
2.1: Understanding how your dreams work
The first step is to understand how your dreams work, the mechanisms when you incorporate events of your daily life into your dreams. You may check your dream diary to find some rules or relationships with your daily life.
2.2 Your current topic
Choose the topic you want to dream about. If you have little experience choose the topic as specific as possible and choose a topic which has a certain importance to you.
2.3. Keep your waking mind busy with the topic
Think about your topic in waking life. Think about it, collect some ideas, daydream, try brainstorming or even a complete different method. Your decision to keep your mind busy with the topic is important.
2.4. Specification and verbalization while falling asleep
Specify your topic. When you are falling asleep you keep your specified topic in mind. Stephen LaBerge recommends to visualize the desired situation. Paul Tholey suggests to fall asleep with the intention to have a lucid dream tonight.
2.5. Patience and persistence for the next days and weeks
Kepe recommends to stay with one topic for at least one week. After that you may switch to an net topic. Psychologist Christoph Gassmann even recommends to dwell on a topic for several weeks.
2.6. Post-processing and execution (if possible)
Now it's about evaluating the dreams. If you asked for advice in dreams you may check if you can apply it.
Chapter about Dream Incubation in the Wikibook Lucid Dreaming
Dream incubation Tutorial by Michael Patrick Kepe (german)
'The Three "Only" Things: Tapping the Power of Dreams, Coincidence, and Imagination' by Robert Moss at amazon.com
'Exploring the World of Lucid Dreaming' by Stephen LaBerge at Amazon.com