One tip that may be effective, is to take a deep breath!
If this doesn't work, remember that there are more homes! A home seller can smell anxiety and excitement, so keep caml and find several houses that you wish to buy. Dont buy into the 'dream home' mentality. Find several homes that fit your needs and ultimately purchase the home where your offer is accepted!
One tip to control your excitement is to focus on the negative! While you should not let this persuade your ultimate descision, you should always remember, that there are more homes available!
Many of your questions should focus on potential problems and maintenance issues. Does anything need to be replaced? What things require ongoing maintenance (e.g., paint, roof, HVAC, appliances, carpet)? Also ask about the house and neighborhood, focusing on quality of life issues. Be sure the seller's or real estate agent's answers are clear and complete. Ask questions until you understand all of the information they've given. Making a list of questions ahead of time will help you organize your thoughts and arrange all of the information you receive. The HUD Home Scorecard can help you develop your question list.