I would recommend starting with some research â€“ look up what kinds of bacteria are typically found in a humanâ€™s mouth or in a dogâ€™s mouth and what types of media these bacteria typically grow on. I would recommend using a rich media to start with that will allow growth of many different bacteria. Rich medias include, for example, Tryptic Soy Agar, Blood Agar or LB (Luria-Bertani) Agar. See the Following link for details.
http://www.sciencebuddies.org/mentoring ... Agar.shtml
Also, I would advise that you read a little bit about sterile technique and include appropriate controls in your experiments. For further information see the following link:
http://www.sciencebuddies.org/mentoring ... ?from=Home
Other options include preparing agar plates using gelatin and beef/chicken broth â€“ see the following link for more information:
http://www.freesciencefairproject.com/b ... teria.html
As for heat, bacteria (especially those from your mouth) typically grow best at approximately 37 degrees Celsius (body temperature).
Prior to your experiment you should consider scientific method:
http://www.sciencebuddies.org/mentoring ... thod.shtml
Remember to state your hypothesis. For example, your statement should be something like â€œa humanâ€™s mouth has more bacteria than a dogâ€™s mouthâ€?
Prepare/obtain the media and use sterile swabs to swab the mouth of a dog and of a human and streak the agar plates.
I think that using 2 people and 2 dogs is a good idea and you should do more than 1 trial for each.
Keep your plates in a warm place for at least 24 hours. You will then be able to count the number of colonies on each plate and can also describe the colonies that grow. If you want to determine that types of bacteria that grow you will need a microscope and further supplies.
I hope this helps. Please do not hesitate to post further questions.