Shakespeare usually followed a standard Elizabethan Five Act Play format when he wrote. In this format, the first act served as the introduction of plot, characters, and scene/setting. The second act contained rising action: those events leading up to the conflict (in a tragedy) or climax (in a comedy). The third act was the conflict/climax; this act represents a turn in power for our central character (described later). The fourth act is falling action: those events leading our central character from that conflict/climax to his or her resolution. And, of course, act five is resolution: what happens to our characters in relation to the plot. Those five acts are all joined by a central character who needs to be intricately involved in all five acts and their specific purposes.
With that in mind, Kate is most likely our central character in TOS (although an argument could be made for Petruchio also). Kate, her shrewishness, and the reason for Baptisa forcing her marriage are introduced to us in Act One (introduction). We see Petruchio meet her as a suitor and his early attempts at "wooing" her for a potential marriage (rising action). In Act three, she is married to Petruchio, and they immediately leave for Petruchio's home (climax, and the change in power from Kate to Petruchio). In Act four, the taming process is in full effect as Petruchio withholds sleep and food among other acts that Kate must accept (falling action). And if Act Five, as the bet reveals to us, Kate is tamed (resolution).