The essential preparation you absolutely need to do to be able to present well (even at short notice) is:
Decide what your presentation will be about. This is also called your topic or main idea. The topics are endless and depend a lot on what setting you're presenting in, and for what purpose.
Create a simple structure based on your key messages which is easy to remember.
Familiarize yourself with your words, stories and flow.
Practice. Take index cards with you just in case, but ideally, you'll know the presentation inside and out by the time you're in the hot seat.
Check you have all the details you need (time and place, timing for your slot, audio/visual support requirements, other speakers, audience profile).