There's been some debate over how to use it. I talked to a VERY experienced pastry chef (my Grandma-in-law) and she said I've been doing it wrong. Here's what she said (for using granulated gelatin, not sheets);
Use a glass jar, and fill it with a cup or cup-and-a-half of tap water. Not hot or warm or cold.... just cool. About 70-80 degrees. Put 1-3 teaspoons of gelatin in there and let it sit for 20 minutes. Swirl it up good (it will be cloudy) and pop it into the microwave. Set it for about a minute, but you need to watch it and take it out as soon as it's clear. The glass will be warm.
She said if you try to dissolve it in hot water, it clumps up, and cold water won't soften it up like you want. Never boil it (unless that is in the recipe).
Well, there ya have it. I've tried it twice now and it works perfectly.
home brewing in Minnesota