Here's where the cookie crumbles. The subject line may consist of a few words but plays the most important role and decides if the person will actually open the mail or not! So while deciding on the subject like keep the following points in view.
Always make sure to keep the subject line short. Keep it less than 5 words
Never use all caps
Keep it in tune with the content inside
Never make it look impersonal if not personal
Add a personal touch if possible. E.g.: Mentioning names
Try asking a question. Questions are more engaging than statements
Never give it a marketing mail sound
Never use 'YOU'. Making use of 'You' in the subject line can make it look like spam
Oops! Never use exclamation marks in a subject line
