What type of business do you want? What skills do you have, how much money do you have to put toward starting and maintaining a new business, what kinds of tools do you have at your disposal? Theres lot of different types of businesses that you can start in a relatively short amount of time. First you're going to want to decide exactly what you want to do, if you haven't already.
Theres basically two types of businesses. Brick and mortar/physical locations, and online businesses. A physical location would be suitable for something such as a medical practice, clothing store, book store, jewelry shop, etc. And these things take much more time and money. So if you don't have resources and cash to throw at something like that, you're most likely going to want to stay away from that at first.
Your second option is an online business. This is where many new entrepreneurs thrive and make their first successful business. Theres a wide open range of possibilities that you can pick from. Maybe you want to be an eBay seller or an Amazon affiliate. Or you could sell custom design T-Shirts. Or maybe if you have the skills you could build and design apps or websites. And if you don't have the skills there's always lot of amazing and free resources online to learn from!
Okay so now, how do you do any of this? You're going to want to really nail down your idea. Make sure you know enough about the business that you want to start so that you're knowledgeable enough to not struggle, and be able to help and answer customers questions if need be.
FIRST You're going to need to do some in depth market research. Are there any competitors? What kind of competitors? What are they doing that you aren't? What ideas do you have that your competitors aren't implementing? What do you think you can improve on and make better? These are the types of things you're going to need to really delve into, and thats just barely scratching the surface. Good market research can take weeks to complete and record all your results.
SECOND You're going to need to put together a half decent business plan. This can be improved later, but its important that you have a basic outline of what you want to do and accomplish. There are lots of templates and resources online for you to utilize if you're not sure what to do.
THIRD Start putting your plan into action. You're going to want to start building out and learning anything new as fast as possible. Take lots of notes and keep process documents. These will be extremely useful later on when you're unsure about something and need to look back to see what or how you had done something previously.
(Assuming you want to start something with relative ease and without breaking the bank, you'll most likely go with an online business. These can be started very quickly and cheaply so you can start making money ASAP. You don't even have to initially register a business entity and just have your website called "your name".com. You can have a payment gateway such as paypal or stripe and have whatever you make from your website go right into your bank account from there.)
FOURTH Okay so now this is where its up to you to continue. Depending on what type of business you have you could go a few different ways. If you're providing people a service, you're going to need to build your site around that and provide them with information about what you do. Or maybe you're selling an information product. You're going to need to build that out and plan how people will be able to access it. Or maybe you're selling custom coffee mugs. You're going to need to find suppliers and have to manage and ship everything. Up to this point I've been using the idea of an online business, but maybe you don't want to do that. Maybe you want to sell T-Shirts out of the trunk of your car, or mow lawns. I can't decide any of this for you, but theres one more SUPER important thing.
FIFTH Marketing and keeping a good relationship with your customers is almost, if not, more important than the actual thing you're trying to sell to them. Whether you have an online business or physical business, you're going to need a good website. A good website that people can access and gain information about you from is vital. Okay so there are a few good ways to market these days. Facebook ADs, email lists, and chatbots. Making sure that you do at least one of these is essential, and all of them would be amazing. Now the way that you get in touch with them is important as well. If they get onto your email list and you spam them with emails to buy your stuff, they're never going to open them and could'nt care less about you and your products. you need to be relatable and open about yourself and what you're doing. make sure that you always follow up and be as helpful as possible if a customer has a problem, because i promise it makes huge difference in the long run.
Hope this helped a bit, good luck!!