Too often, authors misinterpret the phrase "I need to see more" when they hear from editors and agents (and even critique partners). For these authors, they start dumping more "backstory" for their characters, more reasons for why the characters a certain way, more random secondary characters and plots, or simply more scenes that are repetitive to things we have already read. Other authors may even do this to just increase a word count to get their story better positioned to submit to certain publishers.
And all this does is ruin the story.
In fact, a frequent comment I have for submissions that come to me is "TOO MUCH." The author has just overwhelmed me with a lot of things that are not necessary. In the end, the great initial story idea is muddled with so much, we forget about the main character and what really mattered.
The idea of "I need to see more" is give us a chance to make that character more three-dimensional. Let us see other emotions. Let us see "how" the hero and heroine, in the case of a romance, get together. Show us falling for each other. If this is a suspense or romantic suspense, get us into the mind of the detective watching how he or she is figuring out the issues. SHOW us when and how he or she works through those regular roadblocks in the case.
Take the time to go beyond simply the dialogue of the story. Think of it this way. Picture yourself sitting in a staff meeting. You are at a corner table and someone in the room brings up some idea. You listen to what this person says, You might disagree with the person, or agree but don't like the person. What is going on in your head? We don't need to see some scene that happened in college between you and the person. Go with the reactions in the room at that time.
So, your project today is to maybe get out there and start trimming before writing more stuff.