How Not to Begin Your Novel

I recently saw the movie Paris, Je T'Aime on DVD. I'd heard that it was good, but I hadn't heard what kind of movie it was.
I watched the opening scene, and then there was another scene and another scene. Each scene was interesting, but I couldn't see how the scenes were connecting into a story.
The shots of Paris were lovely, and I continued to watch, but I kept saying, "What the hell?"
I figured it would soon begin to make sense.
Eventually, right before I began to pull my hair out, I realized these were a series of very short films. There was no connection at all between the stories except they were all filmed in Paris, and each was some kind of love story. Each short had its own director. All different actors, etc. If only I'd read a review before seeing the movie!
Once I realized I was watching a string of shorts, I stopped looking for how the scenes were linked into a story, and I began to enjoy the short pieces as the little gems they were.
I also liked the idea that I could stop watching at any time and send the DVD back to Netflix.
As charming as Paris Je T'Aime is, this is not a good way to begin a novel.
Even if your opening scenes are gems, they will not engage your reader if they don't give a sense of story with forward momentum.
If your opening page contains the basic story elements (sympathetic character who wants something and who has obstacles to what he/she wants) you buy some time with a reader.
If the writing is good, you buy a little more time.
But, if you don't get a reader to buy into the forward momentum of your story (and by forward momentum I'm talking about something that happens that leads to something else happening that causes something else to happen, etc.) fairly quickly (first few pages) then you will lose your reader.
Paris, Je T'Aime never had the intention of having a central story with a through-line. It is a filmed collection of short-short stories. It's also a great example of how not to begin your novel.