I have been drinking kefir daily for a couple of weeks now and have definitely seen s difference in my allergies and in my ability to tolerate lactose containing foods. This is a welcome change as I have always loved fresh cheeses and dairy products.
I decided to make my own kefir as a quart of it is just as expensive as a whole gallon of milk. I purchased kefir grains from http://www.culturesforhealth.com and reconstituted them upon their arrival. This took 4-5 days. I am about to make my first 'real' kefir. By the way, don't buy your plastic kefir sieve from cultures for health - their sieve is VERY small (less than 3 inches wide), check out Amazon for a plastic sieve of an appropriate size.
I have placed the kefir grains in a pint jar with 1 1/2 cups of milk since I have so few kefir grains (less than 1 TBSP) at this point. I covered the jar with a paper towel and elastic band and placed it in a warm spot in the house, away from my kitchen in which I make bread, yogurt and cheeses to avoid the possibility of cross contamination with yogurt bacteria or yeast from bread making. The kefir will sit for 12 hours or so until it is the right consistency. I had waited 24 hours with the last reconstituting batch and I ended up with a thick yogurt instead of lovely smooth buttermilk like kefir. I'll be checking the kefir periodically to 'catch it' at the right time (I hope). After that, I'll have a better idea of timing. This is certainly a learning process. I'll let you know when (if) it works for me.
Other options include buying kefir from the store and using 3-4 TBSP to create a second batch of kefir, just like you do with yogurt. I may still try that now with the milk I have left from the store. We'll see.