I have a 15m old... she started mini-tantrums at 6m, which included throwing herself to the floor. She does tantrums whenever she really wants something and doesn't get her way.
I talked to a supposed developmental expert at my dr's office a few months ago... when she asked how I responded to tantrums, I said it depends. She said I always should ignore them. I said, well if she is tantruming, and in the process hurts herself, I'm going to comfort her. The dweeb said I should ignore it even in that case. Uh, yeah, child hurt b/c she whacked her head as she was tantruming and I'm going to ignore the fact that my child is now crying b/c she is hurt.
Anyway, my point is, I really do think how you respond does depend. I find if I just 'ignore'.... she only keeps tantruming. Why?? B/c tantruming IS a form of communication and she keeps communicating until she thinks she has gotten my attention. If I go to her, and comfort her and then explain to her why she can't have something and then tell her later (whatever), and THEN let her have her reaction... things go MUCH better. If she then continues to tantrum for an extended period, I usually pick her up, comfort her, and then she get's over it. SHe just needs to know that people understand her.
Anyway, at this stage, none of her tantrums are b/c she is trying to get her way, they are all b/c she is upset she isn't getting her way, and she isn't old enough to express it in a better form. When tantruming, also start labeling the feelings. Oh, you are upset, I understand that... that way they have words to put to the emotions.
Anyway, sometimes, I just completely ignore them if it is something that is NOT negociable... such as, yes your diaper MUST go on. We are putting it on now... and then ignore they wailing, throwing herself, and blood curdling yells. ;-)