ToniVlaic, that's a <i>very</i> complicated question. There are extremely smart people who have spent a lot of time trying to answer that question, and they don't have simple answers.<p>I start with that, because the first reply is "what do you mean by 'works'?"<p>Do you mean that people will use what you've made? Find a small group of people who you think would use what you've made and see if they're still using it after X weeks.<p>Do you mean that people will tell other people what you've made? Check your stats on an invite system, or new signups, or whatever you need to answer this question.<p>Do you mean that you'll be able to market and convert customers at affordable prices relative to revenue? Will you average spending $20 on advertising to bring on a customer who buys $5? Or will you spent $5 to bring in $20 of business?<p>Do you mean "will the thing I made be interesting to the group I'm trying to sell to?" There are many instances where a company made something, found out it wasn't interesting to the group they were trying to sell to, but that someone else found it very useful.<p>Give us more details, and we can give useful answers.