It is important that parents try not to initiate actual toilet training until children are ready. This said, there are various ways parents can work with children who are not yet ready so as to provide them with a solid foundation for future toilet training.
The simplest way parents can lay a good foundation for toilet training is to talk to children about the elimination process in age-appropriate ways. Young children can learn what is in their diapers and how it got there. Older children can be taught how their bodies make and eliminate waste. For example, Mom could start up a conversation while changing her 20-month-old daughter, "Jamie, right now you go poop and pee in your diaper, but soon enough, you'll learn how to go poop and pee in the toilet just like Mommy and Big Sister Sarah."
Parents should take care to label elimination processes using terms they want children to use in conversation. Common acceptable toilet words many American families teach their children include "wet", "dry", "go", "potty", "toilet", "toilet paper", "wipe", "poop", "pee", "pee-pee", "fart, "have gas", "toot", and similar words). Alternative words used to describe elimination are generally either too clinical and formal (e.g., "feces", "urine"), or considered too obscene for use by children. These early conversations about elimination help children to know what words are acceptable for talking about this sensitive subject. They represent perhaps the only time in most children's lives that frank use of potty language is not only acceptable, but actually something to be encouraged.
Parents can supplement their children's early elimination education with various children's books concerning human bodily elimination processes. Such books feature fun drawings and stories to make the topic of elimination interesting for small children, and are widely available in stores and libraries. Elimination books can be featured during children's regular bedtime or other reading times in the years and months before actual toilet training begins so as to familiarize children with the topic. There are also fun children's videos available on the subject of elimination that can be added to children's regular video viewing rotation.
Parents can help their young children to make connections between internal sensations and the elimination process. Children's ability to learn such connections forms the basis of their later ability to recognize the sensations that signal their impending need to eliminate, enabling them to seek out a bathroom and use it rather than pooping or peeing in their pants. To start this teaching process, parents should look for signs that their children will be filling their diaper soon (e.g., children start dancing around, grimacing, touching their diapers, passing gas, or making stomach noises that are not associated with hunger), and point them out to children while they are happening, explaining their connection to the toilet. For example, Daddy could say, "Cheniqua, I see you scrunching up your face, and I smell that you tooted/farted. This probably means you're going poop in your diaper very soon, just like in the book we read last night." Making these connections explicit for children helps them to learn about cause and effect, and how to make predictions about when they will eliminate on their own.
To take it a step further, parents can point out when children actually fill their diapers and explain that adults and older siblings do the same thing, only in the toilet rather than in a diaper. Some parents or older siblings may be comfortable enough to let a same-sex child watch them use the toilet or to see the product and the flushing process afterward. Some children may be interested in flushing the toilet for other family members. This way, they can get used to the sounds and sights of a flushing toilet, and it will be less scary when actual potty time comes. While adult modeling of any behavior is a strong teacher, parents will have different comfort levels in letting children observe them eliminating. Older siblings should always be asked to confirm that they are comfortable with letting younger siblings watch before this behavior is allowed to occur.
While it's probably inevitable that little Suzie will try to sneak a peek at how Daddy uses the toilet, this type of cross-gender observation should not generally be encouraged. First, it may only confuse children to watch the other sex eliminate, as a different toileting process than their own may be demonstrated (e.g., men frequently urinate standing up, while women generally urinate while sitting or squatting). Secondly, it's just a taboo behavior in contemporary America for little children to be encouraged to observe opposite-sex adults' and older siblings' naked bodies. This taboo grows stronger the older children become.
Parent should always take care to keep their elimination-oriented discussions with children positive in nature so that children do not start feeling ashamed of themselves and their bodies. While it may feel completely normal to say, "Pewwww, that's STINKY!" to children while changing their diapers, that type of talk can inadvertently shame children and discourage them from wanting to make waste and to use the toilet. Parents should stay upbeat and excited at the product in the diaper or the potty, and try to smile even if they want to gag instead. This helps children understand that eliminating waste and using the toilet are normal, positive things that "big kids" and grown-ups do all the time.
The topic of elimination is mostly considered to be disgusting and taboo in contemporary America, at least among adults engaged in polite conversation. Some parents may have concerns about being too positive regarding their children's waste products, based on the notion that children may not learn this important taboo if parents don't teach it to them. A positive attitude is recommended to help shield children from thoughts that their parents think they are dirty and disgusting (which will easily lead them to feel ashamed of themselves), and to motivate them to be interested in toilet training and to want to gain control over their elimination at the earliest realistic opportunity. It is perfectly okay for parents to teach their children not to talk about elimination outside the family, if this becomes a necessary limit to set.