Well don’t tease
If someone is holding a gun, it has to go off. It you mentioned an interesting room earlier, go in later. Don’t hint at something if it’s not going anywhere.
Mr Not-So Perfect
Make sure to give your characters flaws. It seems generally its the guy love interest who is completely perfect, amazing at everything, can do anything. Of course you want him to be awesome, but that’s not real life. Maybe you can turn what seems like a nice character trait into something flawed – like he’s really nice, too nice? Too trusting? Or maybe he doesn’t trust anyone and expects the worst from people?
Happily ever after?
Would you want to know what happens to the characters after the story finishes? Do they just finish at The End and disappear, or have you given them a life for the future? I’m not sure how to go about actually doing about this, but it’s an interesting idea.
Make your characters hate you
Think of what the absolute worse thing that could happen here would be. I’m sneaking around a Top Secret Government Facility… oh, and someone spots me. I have to con my way out – I’m from Health and Safety. Oh, I open an alarmed door and security are running through the building looking for me. Oops, I spilt a toxic chemical as I was reaching for the Top Secret Documents. It’s burning some of the pages! Isn’t that more interesting than, I’m sneaking around a Top Secret Government Facility, I find the Top Secret Documents and I skedaddle?