In jazz they have standards that every musician knows how to play. DJs know all the hits that people usually request. As a freestyler you will often encounter the same topics to freestyle about over and over again, so you might as well practice them so you really slay it. You’re not writing lyrics, but practice freestyling on these subjects so it’s easier to get your flow when a big moment comes.
These are some suggestions. The birthday one is super important.
It’s your Birthday
Thank you rap
Flirt rapping with someone in the room
Great party/Party rockin’
Romance/Love is in the air/Toasting a couple
Holidays: Mother’s/Father’s day, Valentine’s day, Christmas, Halloween
Last call at the bar/Closing time
Missing a friend/Fallen hero
Funny people on the street
In the studio