This is a very interesting topic for a persuasive speech, and you will have all kinds of applicable analogies to use to make your point. Unfortunately you do not mention whether you are for or against the idea of parents having to be licensed in order to have children or who your audience is; however, the principles are the same for either point of view and you can adapt to a different audience as needed.
An introduction, whether it is for a speech or an essay really has three jobs to do:
- Capture the attention of the audience.
- Preview the key points which you will be giving in your speech.
- Set the tone for the rest of the speech.
To capture your audience's interest, you will be most effective if you can give them some information they have probably never heard or ask them a question they have probably never been asked. Perhaps you can wake them up with an impressive list. In this case, how about a quick review of all the things people do need a license before getting or doing certain things: owning a dog, driving a car, catching a fish, operating equipment, welding a seam, life-guarding at a pool and hundreds of other things I'm sure you can think of. Whatever you come up with is likely to be less important than being responsible for a human life, so you will already have made your point that it is only reasonable to expect parents to get a license before raising children.
Another idea is to use the site (linked below) to reveal that 51% of people surveyed think people should have to have a license to be a parent; or use one of the examples from the site to demonstrate an outrageous example of bad parenting which would help prove the need for some kind of qualifications (such as common sense and basic observational skills). The kinds of examples you choose should be determined by your choice of tone (below).
Your three (or so) key points will be determined by your research and will comprise the body of your speech, but the points must be previewed in the introduction.
Finally, the tone of your speech, especially this kind of a speech, is very important. It would be very easy to make this a purely humorous speech because the examples could be so outrageous; however, if you want to embrace the humor, you must still present concrete and substantive evidence. Another approach is to avoid the humorous and go for a sense of genuine outrage at how some parents treat their children, and there are certainly plenty of examples of these. The site below gives some horrible examples of parent neglect causing children to die. As one commentator (from link below) says:
The high calling of "parenthood" must be more adequately recognized, respected and honored by our society. Therein lies the future of our nation.
You will have to choose the persuasive language which matches the tone you want to set for your speech, so decide on the tone first.
You will automatically have credibility and relevance if you use examples close to where you live or which have happened to people the age of your audience. If your research is well documented, your arguments will gain you credibility, as well.
This is not part of the introduction, but some things you may want to explore in your research are the benefits of licensing to hold people accountable for their behaviors, using licensing to prevent problems, and the consequences of doing nothing.
This subject has great potential for persuasion, so best of luck!