It’s hard to give advice because it’s such massive subject, I could type all day and not cover the basics.
So I will jump jump into the middle of marketing 101😎
Strategic alliances, think who your ideal customers is..... then think who already serves them.... then contact them and offer a strategic alliance. you will pass on their business card and recommend them if they do the same for you. It will be more difficult for you as you don’t have a proven record but you can offer an incentive.
So if you are going to offer a oven Cleaning service then contact carpet cleaners and ask if they will allow you to contact their existing customer list offering your service. They will agree because you will pay all the cost of contacting them but they also get to mention a special offer they are giving.... it’s a win-win situation