go with the flow...use good/ strong/ precise vocab
and do some research about the possible...ya know, subjects.
annnnd body language is imporant too haha
hope i helped
haha i do forensics, i went to state in impromptu speaking
so the thing is you need to have a structure in place
also, know the subject range, what's likely to appear
and familiarize yourself with it.
have a few good quotes in your head that will fit general speeches.
a good structure is an introduction, then three body points, and then a final summary.
make sure that you put your weakest point in the middle because it's less likely to be noticed in that position.
Cant really help with impromtu since the topic is given at the time of the speech. To be great at impromtu you need to be able to think on your feet, which cant be taught, and a general base knowledge of a lot of topics to use in your speeches.
Read classic books, watch classic movies or refer to historical movements or events. The people that do these things are mad smart because of the preparation
i do that also, and what helps me is be confident, never say um or like, always have good eye contact, and really prepare for it and be ready for it. Try to relax and don't be nervous. If you do those tips you will be good, prepared, confident, and be succesfull!