For me, one of the biggest challenges in a novel is writing an effective opening.   Sometimes they just work, but it seems that I can never make it work on purpose.  In an attempt to tackle this problem, I have enlisted the help of my online writing workshop and collected a number of elements that have to be present in an opening of a successful novel:

1. A catchy first phrase — but, importantly, one be backed up with what comes after.  This phrase serves as a promise, and the novel must deliver on the promise by matching the quality of the later text with the quality of the opening phrase.

 2. A brief but vivid sensory input of the setting that places the reader right into the story.  Ideally, the description should be given through action, as part of the plot, and it should move the story forward

3. A brief but catching introduction of the main character that makes the reader strongly relate to this person and care what happens to him/her

4. Tension in the story, ideally through action or suspense.  This tension doesn't necessarily have to be the main conflict of the story. Rather, what you really want to do is create an anticipation of events in the reader.  My workshop members add that you emphatically do not need peril or action in the first paragraph or page to engage a reader. Sure, you can use it, but it's not necessary — and more often than not, it doesn't work.

What you do need, is at least one unanswered question, and something to compel the reader to want the answer. To get that answer, they flip to page 2, which maybe answers the question and maybe doesn't, but probably presents more questions that will need answering as well. Call it "dramatic tension" as opposed to "plain old tension."

Importantly, while this checklist seems to cover all the necessary elements, it comes with an additional challenge.  You should have an opening that draws the reader into character, setting, and problem SIMULTANEOUSLY.

My workshop members further recommended to read Nancy Kress's book 'Beginnings, Middles and Ends'.  Her checklist of things one needs to catch the attention of a busy professional is:

Character – a person for the reader to focus on, an individual not a type.

Conflict – subtle or overt, it must be there.

Specificity – effective use of details, which, in her opinion, is the one most important mark that distinguishes publishable manuscripts. 

Credibility – prose that can be trusted. Credible prose by itself is not enough if the story is dull, but the lack of credible prose can be fatal.

She also speaks of the 'implicit promise'; this will be an intellectual and emotional promise telling the reader what sort of story to expect.

So far my own research has turned up three types of openings:

1. A wittily told background of a character ("Mr. and Mrs. Dursley, of number four, Privet Drive, 
were proud to say that they were perfectly normal, thank you very much." Harry Potter)

2. A description of a setting that creates atmosphere and is told in strong, dynamic words 
("The snow came down so thickly, it formed fragile snowballs in the air that tumbled and melted 
as soon as they landed on the horses lined up along the dock."  Nation, by Terry Pratchett)

3. An immediate plunge into the character's POV ("One of the few redeeming facets of instructors, 
I thought is that occasionally they can be fooled" — Another Fine Myth, by R.L.Asprin. Or, for a 
non-first-person: "Sam Vimes sighed when he heard the scream, but he finished shaving before he 
did anything about it" — Night Watch by Terry Pratchett)

There are also openings that immediately plunge into action or dialogue, but I classified them as 
a variation of #3.

I am still working on the subject – and struggling to create a perfect opening for my novel-in-progress that truly encompasses all these elements – so any comments, suggestions, or additions to the list are really welcome.