It's the end of the festival and regardless of having a film screen or not, you still need to do some follow-up.
Were you looking for crew and maybe cast members? If your film was screening, did you meet any other programmers and/or sales agent/distributors? Is your script shoot ready and looking for financiers or assistance with funding?
By this time, you have collected business cards and made new industry friends. Depending on where your new contacts are coming from, wait a few days so everyone can recuperate. You should be aiming to keep in contact with everyone local so you can grab a coffee and talk all film. Someone in the industry always knows someone else who knows someone else who could help with the next festival or sale. If the current festival you have just attended is in your hometown, check out what they have year round. Maybe they have collaborated with a fellow festival that can propel you forward. Use the business cards you have collected.
Still not sure about how you can maximize your post-festival experience? Email me at firstname.lastname@example.org