Following are some observations I have made over the number of contests I have judge, consistent errors that detract from otherwise excellent entries. These are also factors I take into consideration when editing my own work and critiquing the work of others.
1: Dangling participles. (Walking to the store, the car nearly ran me down. Walking is the Participle. With this structure, the car is the subject, so we have a walking car.)
2: A shocking misuse of commas.
3: Too much telling.
4: Not enough use of the five senses.
5: No sense of time or place through dialogue, description, or tone.
6: No sense of the main characters' goals or conflicts.
7: Forced conflicts—anger and distrust with no logical reason for either.
8: Heroine being physically attracted to the hero regardless of how nasty he is to her. (This may be realistic, unfortunately, and it's not emotionally healthy.)
9: Huge chunks of detailed descriptions without any purpose.
10: Too many point of view shifts in a single scene. (Even if you put in the space or ***, going back and forth every other paragraph is still head-hopping.)
11: Reaction occurring before action. (He jumped when she covered his eyes with her hands.)
12: A lack of hooks at the end of the scene.
13: This is especially important in The Royal Ascot: easily verifiable historical errors--British titles used incorrectly, hero or heroine the brother or sister of the other's dead spouse, anachronistic behavior.