Don't do that.
I don't mind if my friends text me or call me up on the phone. . . or even if somebody I don't know well emails me to tell me something important. I don't even mind ads, when I run across them in the wild. However, I mind VERY MUCH if telemarketers call me specifically and interrupt dinner. You get the distinction?
BUT I WAS TOLD I HAD TO GO ON SOCIAL MEDIA AND PROMOTE MY BOOK!!!
Social Media of all kinds, including/especially Twitter, is all about. . . well, being SOCIAL. It's about connecting with people on a human level - not about YOUR BOOK YOUR BOOK YOUR BOOK - but about, like, how your dog caught an opossum or you are worried because your fire alarm seems to be haunted by poltergeists, or you need to find the best Chinese restaurant in rural New York. When, in the course of talking about mundane things, you also mention YOUR BOOK, it doesn't come across as sleazy - just as a part of your life, which it is. People are significantly (like scientifically 100000%) more likely to want to support you if you come across as a genuine, cool human being who also writes books, rather than a spam-machine-robot.
When you start a twitter account from scratch, it's almost like you are standing alone on an overturned apple crate in the park and speaking into a home-made paper megaphone. You have no audience yet -- you are just a lone soul standing around talking to the air. If you're lucky, you have a few real life friends that will start hanging around you. If you're entertaining, you'll get a few more, and they'll stick around. Soon you've got a nice little crowd going. Awesome! You get off the crate and start interacting. Now it's not you being a nutbar and talking to the clouds - it's you engaging with your group, having real conversations, cracking jokes, sharing ideas about things ranging from celebrity-silly to philosophically important - and occasionally one of you whips out the old paper-megaphone again to talk about a pet project or something, and nobody really minds, because hey, you all know where each other are coming from. Wheee!
If, instead, you use your crate as a platform from which to throw garbage at people . . . well they are REALLY UNLIKELY to want to stick around for that. If you start targeting people specifically -- that means you @mention their names and barrage them with advertising even though you don't know them -- they are likely to report you for spam and your platform will get taken away altogether.
And it should go without saying - don't HIRE somebody to do this on your behalf, either. It's a waste of your money, and it will give you a black eye with the potential readers and bigmouths you probably want to impress.