How to train for triathlons?

Read up and plan. Check out the books in the bookstore. Triathlon training by michael finch and the triathlete's training bible by joe friel are good ones. You need to be trained in each discipline first. Then try 2 in succession. This is called a "brick" workout. Usually it is ride/run. I use a 5:1 or 4:1 ratio. I.E. Ride 20miles/run 4 or 5 miles. Start slowly, build up and follow the plan. Race the way you train.