Google adwords. If you don't know what you're doing they'll send you bankrupt. It's a great way to spend money, but, without good knowledge of how to build campaigns that work, your results will be poor.
Google business page. A MUST! Equally as important as a website. Why? When you do a search for a product or service and there's a list of 3 at the top of page 1, that's Google business pages. It's a simple way to get your business on page 1 with less effort. Again, it must be done right.
Yelp, Manta, etc, etc. This is where it become geographic and demographic driven. Except maybe Yelp who I wouldn't pay a dime. Somehow they've wriggled out of every lawsuit brought against them, but I don't believe they're even mildy clean - forget squeaky! Certain websites work better for certain industries. I know a number of contractors and even service people who swear by Thumbtack. Personally, it didn't work for me. Same goes for Angies list, though they seem to have declined in usefulness in recent years.
Facebook ads (the FB equivalent of Google Adwords) are really good for some, with the same "send you bankrupt" (albeit, currently at a slower rate - they're cheaper) disclaimer. I have a client in NorCal who does paint parties who just posts in regular old FB feeds and gets great results.
I belong to a BNI chapter and referrals from BNI make up 25-30% of my portfolio. There's hardly any business that won't be a fit for that.
For me, it's about doing what you're good at, and getting professionals to do the rest. Everything has become so specialized that the old-style business owner who did marketing, HR, payroll, accounting and everything else, as well as actually being the technician, is gone. There's too much competition and you can't afford to start building your business from behind the 8 ball right from the get-go.
I hear it often, "I built my website myself and saved a ton of money." Yeah, no. When I look at these websites they're almost all badly built, poorly optimized and give the visitor a horrible experience. Plus they're on page 10 on Google or worse (because the builder had no idea about on-page SEO) so they'll never be found anyway. Yes, you may have saved money (if you don't take into account your own time which you could have better used to be working what YOU do well), but you've used it to produce a tool that's useless.