You may hear stories about mother whose children are completely potty-trained after only 2 weeks, but these tend to be exceptional cases. It can take up to half a year for a child to be completely clean, though girls tend to get there a little bit sooner than boys.
When can I start trying to potty train him?
He's ready to start as soon as he regularly indicates to you that he has a dirty diaper. It doesn't hurt to try them before this, though, as some children will take to it quite easily.
How do I start?
The whole idea of potty training is to teach your child to use the toilet or his potty instead of his diaper. The goal is that he should stay dry and clean both during day and night, though it takes a little longer for them to get the hang of being night-dry. It can take a LOT of time and energy, and therefore is advisable to start when you can keep an eye on him or her 24/7, for example during a holiday or during some time off work. Many toddlers will begin when they go to nursery or kindergarten; they'll notice other children going to the toilet and this can be extremely motivational.
Preparing your baby.
Your child learns by observation, so take her to the toilet to show her how you use it. You can also explain what you're doing there. Get them involved by letting them flush the toilet or give them the toilet paper to hold for you.
Start with the potty
It can be easier to start with a potty rather than going straight to the toilet. Put the potty in a place where your child likes to play and sit him on it without his clothes or diaper on. This way he can get used to it. Once your child has finished doing his first toilet then praise him, get excited and let him see how proud you are of him. If you do this every time he will be very encouraged and want to do it to please you. Once your child has started to pee on the potty, progress will accelerate from there. Before you know it he will be using it every day voluntarily. The first time you take toddler out without a diaper, make the trip a short one.
Some children are quite nervous about pooping, so it may take longer for them to do so in their potty or the toilet. Encourage him, but don't try to force it.
Always stay near your child when they're on the potty or toilet; talking to them or reading to them, or playing a game, can make it more fun for them. Don't forget to celebrate with them every time they are successful, but don't let your disappointment show if there is no luck now and then.
From angelababy In Q&A