Leave your timer at 10 seconds for photos
Just change it. JUST CHANGE IT.
Make long, repetitive, boring stories
The secret of Snapchat -- of all social media, really -- is that your life is not as interesting as you think it is. It's probably pretty boring, actually. That's a big part of being a self-respecting person: instead of spending your entire paycheck on vodka and skydiving, you buy sensible stuff, like really cute salad bowls from Etsy, or a shower curtain.
If you're a young person full of light and hope, you're probably all like, "nah." Deny it if you must, but eventually the banality of existence will swallow you whole. When it does, hopefully you'll have the good sense to keep it off Snapchat. No one wants spend 200 seconds living your boring-ass life with you.