An introduction is not a warm-up lap. It has five jobs to finish, usually in well under a minute, and every job you skip becomes a more expensive problem later in the speech. Set your speech length, switch jobs on and off, drag the seconds, and watch both the clock and the bill.
1 · How long is the whole speech?
2 · The five jobs — toggle, then drag the seconds
3 · The conclusion
ConclusionClosure signal, restatement, one-sentence summary, clincher0 s