Selam aleykum

Hard question without a background. Some things you should consider when choosing your topic: Are you going to give the lecture to muslims or non-muslims?
Muslims Alhamdulilah
Do they have some basic knowledge of Islam?
Yes they do
Are they already interested in Islam or not?
Yes of course,its a meeting i have with sister who wanna learn n gain knowledge,so yes Mash|ALLAH they do
Do they live in an Islamic country?
not by any means...although there are alot of Muslims Alhadmuliah..america
Where will you be giving the lecture? In school?
little group..wow,at school i wish...that would be so cool but so hard.since majority believe were all terroriest.although some are open minded
Is it a catholic shool, public school?
not a school
Will the teacher allow you to pretty much go anywhere or should you be ready and anticipate replies? Is the group mixed gender?