While its easy to find a 'most profitable coin' by going to
www.coinwarz.com or
www.whattomine.com, you can also get lucky by trolling the new altcoin announcements right here in bitcointalk.
Find a new coin in its infancy, just hatched... and you can be lucky enough to get a heap of coins before they even hit the market. Sometimes there are coins that are even more profitable than what is shown at whattomine, etc.. you just have to be willing to take the risk and have to keep up with the latest releases
This to me is what makes mining exciting, the speculative mining aspect