Chances are, if you think your idea is original, it isn't. You will need to do a lot of research to make sure that nobody else is currently doing what you are doing. Even then, you will have to consider that somebody, somewhere, is also thinking the same thing you are, and at that point it's a race to see who can get the patent andor copyright first.
1. Modify An Already Good Thing
Even if you don't have your own idea, you can modify someone else's pre-existing idea. For example, many people like popcorn but want butter on it. Origionally, the only way to get butter flavored popcorn was to literally heat butter and then dip or spread the butter over the popcorn, and this required putting butter into a pot or bowl and melting it over a stove or in the microwave. Eventually, popcorn makers had built-in repositories to place butter so that as the hot air passed over the popcorn kernels, popping it, it also heated the butter so you didn't have to dirty a separate dish. Then, someone came up with the idea of coating kernels of popcorn in a butter spread so that they butter themselves as they pop. Of course, the idea was very messy and unusable in hot-air popcorn poppers because the butter would drip down into the machinery, so instead, a foil bag was provided to contain the buttery explosions and, as it turned out, double as the bag you could eat the popcorn out of (assuming you didn't then pour the popcorn out of the bag and into a bowl for eating). Always think to yourself, what's the next logical step? What doesn't change the product itself, but might make it faster or easier to use?
2. Avoid Impractical Ideas
If you stumble upon something that has a lot of potential, be sure to evalute how realistic and practical it might be. For example, you might come up with the idea to manufacture something, but there ends up not being a market for it. You might think kids will love your particular product, but then parents don't end up buying it, or you have limited success but your product gets known as a fad at best.
3. Do Market Research
The best thing you can do is actually get out there and talk to potential customers. Never be afraid to ask them what they want. At the same time, you will get a general sense of how many people out there might be interested in such a service.
4. Find A Niche
Let's face it, youre not going to be big. You don't have a lot of capital, nor do you have a big advertising budget. You don't already have a million customers so you can't price your product less and still make a profit because youre still getting a little bit of money from each customer. What you can do, however, is find a niche market. You might know what industry you want to work in, and that's about it - now's the time for you to narrow your options and cater to a specific type of customer.
5. Get It On Paper
Once you have an idea, it's time to flesh it out into the most basic elements - products or services, suppliers, customers, and work. For example, if your idea is to provide web design for small businesses, then this is where you need to sit down and figure out what suppliers you might need (web hosting, for example), and what services youd be providing for customers. Think of it as inputs and outputs. The next step, of course, is to determine a price that is profitable.