Place. Once you've signed a contract with a publisher, you have no control over where the book is distributed. However, you do have some say as to where you place your book -- meaning where you decide to submit the manuscript. Let's suppose all your dream publishers, let's call them the Tier 1 publishers, reject your manuscript. You now have the choice of sending it to Tier 2 publishers. It's your product, and you get to make the call. Before you leap, do your homework . Think carefully about how selling to any publisher aligns with your long-term goals.
Promotion. No, you don't have control over a publisher's promotional efforts. Yes, you do have control over what you decide to do promotion-wise, given your budget. I won't touch the specifics of any particular promotional efforts. However, I will correct the misconception that the goal of promotion is to increase sales. It's not that simple. Your first goal is to increase Awareness. In large corporations such as the one I work for, market researchers conduct trend studies to determine a product's (or brand's) purchasing strength with customers. The flow looks like this: Awareness, Consideration, and Preference. As a writer, you can influence awareness. It's a saturated market out there, so what can you do that will be effective? The old adage that word of mouth is the best advertising is true. Unless you can score a spot on Oprah, the best buzz arises out of ... the product itself.
Product. As a writer, you have quite a bit of control over the story ~ at least until you get a revision letter (one that hopefully makes your story even better). To create buzz about your story, you need a high concept (a plot that is immediately apparent to the editor/agent/reviewer) and a unique twist on a tried and true plot. Does having a high concept with a unique plot really work? True story: at a recent regional conference, I sat next to an agent at dinner who asked me about my book. I gave her the tag line and she gave me her card on the spot.
A high concept plot is only part of the story. Now you have to grab readers with compelling characters with whom they can relate. Make your reader care, laugh, cry, and gasp. And deliver on your promises. Easier said than done, but think about those books on your keeper shelf and ask yourself what differentiated them from all the hundreds of other books you've read.
All of the 4 Ps of marketing matter, but Product matters the most. The story is the most valuable marketing tool you've got.