Web API authentication like Facebook, Twitter and Google

I need to develop an external API, and I want to implement authentication with a client ID and a secret key just like Facebook, Twitter, Google and Microsoft do.

I have read some tutorials about OAuth2, but his generated token is temporary, and clients need to pass the username and password to get a token.

So, what I want is to give a client ID and a secret key to every client that will use my API, and they should pass this data on every method they call. Before returning the result, API checks if the request is valid.

What is the best way to do this?