Attention-getters contain anything that will arouse the interest of your audience when giving an address. For instance, some speakers enjoy beginning with an anecdote -- a short story or tale -- to help establish their larger point.
Others will begin with a quote from someone who is more famous than the speaker, while still others opt to begin speaking with a familiar verse or excerpt. In any case, the attention-getter should do exactly what it claims to do: it should make your audience sit up and take notice.
Attention-getters in speech are a lot like ledes in print news stories. Both are engineered to grab, or "hook" their respective audience. With practice, an effective speaker will learn exactly what attracts the attention of his/her audience the best.
An attention getting is the opening to any speech. It is a way of, well, getting your audience's attention. There are several different types of attention-getters.
A story- a touching or humorous anecdote
A rhetorical question- something to get the audience thinking
A quotation- possibly inspirational
An unusual statement- something shocking that jars the audience to attention
Humor- a joke (this one runs the danger of not being funny)
Shocking statistic- a number that is surprising
Any one of these options would work well for an attention getter. Try writing one of each for your speech, and then choose the one you like the best.