I've been making my own yogurt for more than a year and like it a lot. Generally, for plain yogurt, I just follow the directions that came with the machine I use is a Salton 1 qt. machine. You will need an instant read thermometer.http://www.amazon.com/Salton-YM9-1-Quart-Yogurt-Maker/dp/B00004SUHY/ref=sr_1_9?ie=UTF8&s=home-garden&qid=1268164557&sr=8-9
For my children, though, I have experimented with making flavors in various ways... They are picky, though, and prefer to have smooth, thick yogurt (like the stuff in the stores). Nearly every kid brand out there has high fructose corn syrup in it, though, so I've been experimenting with gelatin. The newest family favorite is made using packets of jello:
1 qt milk
1/2 c. fresh plain yogurt (with live cultures)
1/3 c. powdered milk
1/6 c. jello, any flavor (1/2 packet)
1-2 T. sugar or honey (optional)
Take plain yogurt out of refrigeration and allow to warm to room temp. in a small bowl... stir it to make it smooth.
In a medium saucepan, mix milk, powdered milk, jello and sugar or honey (if you want a sweeter yogurt). Using a medium heat, bring to 180 degrees fahrenheit, stirring continually. (If you have problems getting the ingredients to dissolve, use a whisk). Remove from heat and allow to cool to 110 degrees (I use a cold water bath to speed up the process).
Stir in the yogurt with live cultures gently. Pour all into the yogurt machine and let it stay for between 4 and 12 hours. The longer it stays, the more tart the flavor. I usually leave it about 6 hrs. If your yogurt hasn't set up by the time you plan to stop it, give it another hour and it should be thick.
Place in refrigerator until well chilled... enjoy.