At 2.8, he may not be ready yet. It should come soon, but readiness involves the physical ability to recognize urges and respond in time, or hold back if necessary, the cognitive ability to weigh the advantages of using the potty, and the emotional desire to attain a new and important goal. These do come together for virtually every child, and they become as eager to potty-train as they were to learn to crawl, walk or talk.
Here's an extremely helpful website you might find helpful. It gives a few variations on"readiness" checklists, plus tips on various training strategies, the best ages to start them, and the advantages and disadvantages of each approach: http://www.parentingscience.com/potty-training-tips.html