Dialog Analysis
How is the pace of the conversation? 
Is the scene calling for a quick pace as in an action sequence or a more conversational pace as in a sit-down-over-coffee situation?
Is time and place consistent with language?
Does the language being used by each character meet the character's time/place/characteristics of the character and the story's time period?
Are you using slang? 
Slang can date a story so it is worthwhile to make note of any slang used in your story. If you are writing a period piece, make sure the slang is relevant to the time period. 
Does the dialog mesh with the characteristics of your character? 
In other words, if you have a thoughtful character, does the pace of the dialog reflect a more meditative style of speech?
Does the dialog move the story forward? 
If your dialog is not revealing something about your character, the setting, or the plot, consider whether or not you need the dialog at all.