Before you start a freestyle, figure out your “talking points” — ideas and phrases you want to repeat to your listeners. You can freestyle about whatever you want, but keep coming back around to the talking points.
We learned this technique from politicians and spokespeople. They decide on the talking points for the ideas they want to promote and reinforce. When they are giving speeches or talking to the media, they keep returning to these points, no matter where the subject of the speech goes, and no matter what derailing or baiting question they are asked by a reporter. If you listen to them, they might not even be making sense, but they definitely communicate their talking points, and their message comes across loud and clear.
This technique is used by a lot of rappers to communicate their stage persona which is important to their whole image. You can use it if you are ever asked to freestyle at an event with a purpose, either a birthday or theme party, or more importantly, an activist event. Remember to learn their talking points before you freestyle, and use them. The promoters and organizers will love you.