I haven't been making yogurt much lately, although I had had some success with Seabird Chronicles' method. I would have a good batch, then a couple of so-so ones; and in between I had to clean the pint canning jars I made it in (yuck). With a bottle brush. (Have to get me some wide-mouth jars.)
OK, enough whining?
Anyway, I think part of the problem with inconsistent yogurt results might just be the kind of yogurt used as a starter. I've always tried to get natural brands (I know yogurt with additives won't work well), but as I said I've had varying degrees of success. I bought some Perth County brand yogurt last week (sorry, that one's just for Ontarians), liked the taste, and froze some to use as starter. I made a batch today and it's probably the best-textured, least slimy or strange, most acceptable yogurt-that's-like-yogurt I've made in a long time. I don't THINK I did anything different--just followed Seabird's instructions and let it set on a heating pad for about six hours--took the jars out and let them chill in the fridge for awhile before I dumped them out into a larger container (maybe that helped too).
Or maybe the very strange weather we've had (cold, hot, thunderstorms, sunshine, bouncing back and forth), that's played havoc with all my baking lately, is good at least for yogurt making.
P.S. Crayons calls the heating pad "the yogurt maker." I explained that it wasn't actually designed for that, that some people actually use a heating pad for sore backs. She thought that was very funny.