What is an ICO?
Initial Coin Offering, basically a pre-sale of a new cryptocurrency before it is traded on exchanges. The idea "ICO" is a merger of IPO (Initial Public Offering) and a Kickstarter crowdsourcing campaign. Use Bitcoin or Ethereum to buy new coins at predetermined prices before they are available at market.
How to find an ICO?
Search the developers. Who are the founders? Avoid teams with anonymous developers. Read the white paper. Do your due diligence. Do your homework. Does the project have a good team? Do they have a good idea? Do they have a good product? How is the competition? Will you get your coins immediately? Do you need to use an escrow account? Do you need to be an accredited investor? Is there a prototype? If so, does it work? How long until the coin will be listed on an exchange? Does the project save coins for future development? Is there a working wallet for the coin? Does the coin have a solid community around it? What are their values? Is it an app, a platform, a protocol? What is your expected return on investment?
Some ICOs are capped. Some ICOs have no cap. Some sell out immediately, others are open for months. Some require you to be an accredited investor.
Some ICOs have made great gains. Others have been straight up scams.
You could also pass on the ICO and wait to buy after the coin is listed on an exchange.