Someone (you know who you are) asked me to have a look at this proposal to bombard a SF mag editor with submissions from women on a single day. It sounds unprofessional and I wouldn't do it, but that's me. In all things publishing, do what you think is best for you.
What is best, anyway? Go to all the cons, do a hundred signings, buy these widgets, put an ad in this rag, charm this editor, get that reviewer to write you up, have a book video made, buy this sort of web site, get in with the right sort of group blog, do this kind of mailout, podcast an interview, buy your book in bulk at the right stores, hand out ARCs like cigars, generate as much buzz as you can and at the end of the publishing day you may be a huge bestseller, or you may utterly fail, or you may fall somewhere in between those extremes. Probably the third.
There are no guarantees. There are no proven shortcuts. There is no secret handshake.
I think everyone who is comfortable with the idea of self-promotion should try some of it to find out what they're good at and what they like doing. There is a lot you can do for free (blogs, signings) or at very low cost (web site, book giveaways.) As long as you don't get into financial trouble and it doesn't interfere with the work, give something a whirl. That something might work nicely for you.
But if you find that you don't like any of it, or it doesn't work for you, or you can't afford it, and you decide to stay home and simply write, that's okay. You're not a failure, and you're not cheating yourself of success. Publishers will not hate you because you're not out killing yourself to sell. I speak from experience.
So the next time someone is yelling at you that you need to do this or you have to do that, remember that all writers do not sell, promote, publicize or package. We are not all guest speakers, book signers or workshop teachers. We are not all buzz generators or hype-junkies.
The only thing all writers do is write. That's the entire job description. Everything else is optional.