There are plenty of write-ups on how to assess the viability of your business idea but here is my fairly simple take on it. Can you write a simple vision statement for your idea in the following format: “Our vision is to be the most useful X for individuals/companies who Y”, where X is your product/service category and Y is your target customer description?

This seems a simple question but itself begs a couple of other questions:

• Does your product have a particular target customer type and can you describe this customer type simply?
• Do you understand what would be the most useful product for your target customer type, will your product/service make the grade and do you have the knowledge, resources and commitment to do what is necessary to help your product/service into the most useful thing for your customers.

Now let’s apply our vision format to a few well known businesses/products to get some examples:

• Google Search: The most useful website for people searching for information on the Internet.
• Ebay/Amazon: The most useful website for people looking to buy/sell stuff online.
• Volvo: The safest cars for safety-conscious car buyers (just to demonstrate a variation) 

One last thing, as a startup, you should aim for ideas where it is relatively easy and cheap to reach your target customers for marketing purposes. So if a website exists already where your target customers hang out, that is great - because it means you can hang out there too and tell them about your product or if it came to it advertise there.

So if you are interested in building a really big business, test your idea first by attempting to answer the questions above. If you struggle to answer them, it may well be a sign that your idea will not turn out to be as big a business as you would like. As always, wishing you all the best with your business ideas.