I potty trained both my boys just before the age of two, which is quite early for boys. Here's how I did it.
Step 1: Prepare
Before training I gave my boys the chance to walk around the house with no nappy on so they could see where the wee comes from, but without any pressure to achieve anything. I remarked on the wee, cleaned it up with no fuss or scolding and mentioned that I put mine in the toilet.
This might sound like wanton carpet abuse, but when you toilet train your child, your floors will eventually get wet or (horrors!) dirty. Out of love for my floors I usually waited until the boys had already done their morning poo and gave them just an hour or two with no pants.
Step 2: Concentrate
I chose a week when I had nothing much on, and planned to pretty much stay at home for a few days and concentrate on the training. If you take a child out and distract them with sights and sounds they are likely to forget all about the potty. I also generally left the TV off, as it really hypnotises them and they don't want to do anything else but stay glued to the sofa.
Step 3: Demonstrate
At my first son's daycare one of his little friends was trained just before him. This was really lucky for me as he knew exactly what was required. He also knew that lavish praise follows potty success.
When my second son was ready to be trained, his big brother was almost four years old, and was delighted to help me by giving a demonstration of his potty skills. The little potty novice watched as his brother sat on the potty, did his wee, and received praise and a sticker for his chart.
The 1974 book "Toilet Training in Less than a Day" by Nathan Azrin and Richard Foxx recommends using a doll that wets and letting the child help you train the doll before they try the potty out for themselves.
Step 4: Get on the pot
The first wee that goes in the potty will be more or less accidental rather than controlled by the child, so they need to sit on the potty for a good while. I got a stack of books and a couple of juice boxes, and sat down on the floor next to my son. He sat on the potty and drank the juice and I read him book after book. Eventually, out came a wee.
I had a nice big, comfortable potty and my boys did not mind sitting on it. If your child is not keen on sitting on the potty, then you will need to take it back a step and gently encourage them to sit down, praise them for doing it, and try to get them to stay a bit longer each time.
Step 5: Celebrate
When that first wee wee landed in the potty there was great joy. I congratulated my boy, admired the wee wee, lavished hugs and kisses on him, and after we'd put the wee in the toilet and flushed it away, I gave him a sticker for his chart. He was thrilled, and really wanted to do another one.
Step 6: Don't forget to remember
After that first direct hit, I told my son if he felt another wee, or indeed a poo, coming he should sit on the potty and try to get it in there. Of course, this is expecting too much, so I put him in pyjama trousers (easy and quick to get down), we played for a while, he drank more juice, and after a while I got him to sit on the potty again in the hope of catching a wee.
More celebrations followed the potty hits, but no scolding for the misses. Every puddle on the floor brings them closer to understanding what it feels like when the wee is coming. For the next few days I got him to sit on the potty regularly to see if a wee would come. After a while I just had to ask him if he needed the potty, and he would know if he did or not. Eventually he was able to do a wee voluntarily, for example just before bed.
For poos, I watched closely for that special facial expression and posture that tells you a dirty nappy is on the way. Yes, we had a couple of very unpleasant accidents but, again, no scolding was done, and after day three both boys were potty perfect.
Step 7: Pants
Underpants are not really essential but I found them useful on two counts. First, my son was happy to have grown-up pants, and he was motivated to try to keep them dry. Second, when he eventually did a poo, the underpants contained it (more or less). I bought really cheap undies from the supermarket, so these soiled ones went in the bin, not the laundry.
After this I stuck with the underpants and did not use nappies again except for naps and night time. Once he was able to do a wee voluntarily I felt ready to take him out for short trips, armed with a bag full of dry pants of course.