With both of my children we did the potty training at their own pace. With my daughter she sat on her toilet whenever I would go to the bathroom. We started this when she was 12 months old. At about 14 months I would take her diaper off and let her go, she never did. At 15 months (I was due with my second child any day) I sat her on the big toilet and she went. From there on I let her be naked when we were at home and just placed her on the toilet every hour and gave her the oppurtunity to try to pee. She was completely day potty trained at about 20 or 22 months old.
Now middle child, my son is current 2 years old. He one day walked into the bathroom pushed me out of the way and climbed up on the toilet and peed. He was 17 months old. I think having watched everyone use the toilet helped him realize this was something he wanted to do as well. He just turned 2 and we are working on the potty issue as well. He runs around the house naked or with underwear on, but I find that it works better naked. He does not have to sit on the toilet, nor does he have to stand next to it, instead he created the way he would go, which is crawling up on the toilet and squating to pee or poop.
My advice would be not to put pressure on the child. If you make this a control issue then it is going to become a power struggle. Instead make it a game. Every time he goes in the shower, say "no" firmly or "STOP" (I do this anytime I catch my son having an accident) you would be surprised at how they are startled and will usually stop. Then tell them that we go pee and poop on the toilet and place him on the toilet. Just keep doing that and things should go well.
But remember too that each child developes differently and is ready to beginning potty training at different ages. I truly believe that there is not a certain age that a child should be potty trained, but I do believe that the parents need to pay attention to the signs of a child being ready to train.
Good luck. And I hope this helped a little....most importantly, make it fun, reward for sitting on the toilet (or squating) and/or going to the bathroom, and do not pressure the child.