When is it Time to Start Potty Training?

Potty training your child is never "easy," but you can make it a lot easier by planning ahead. 
 Step 1
Talk with your child's pediatrician and read one or more parent resource books.  There are many ways to potty train and this will help you better understand your options.   I would start with the American Academy of Pediatrics guide to toilet training by Mark L. Wolraich.
Step 2
Understandably, parents want their children to complete this milestone as soon as possible. That being said, children will be more likely to succeed if they are in a nurturing and responsive environment. It is better to wait if your child is going through stressful situation i.e. moving, parental divorce, travel, illness, etc... 
Step 3 
Before you consider potty training your child you will need to assess their readiness.  I would recommend taking The Potty Training Readiness Quiz, by Elizabeth Pantley from the South Carolina Department of Education.
Step 4
Acknowledge that caregivers, teachers, nannies, grandparents, and school administrators have a significant influence in your child's life. Continued communication that is open and accessible should be the foundation of each relationship. For that reason, you will need to schedule a time to meet with others before you begin potty training.   Consequently, your child’s developmental and emotional needs will be better supported when everyone is working towards a common goal, and is consistent with their choices.  
Step 5
Books are a great way to begin a conversation with your child about potty training.  So, read, read, read! Remember, you are your child's most important teacher and what you say does matter.
Step 6
When everyone is on board (including your child) choose a date to begin.  Start the process when you can stay at home a few days and focus your efforts. 
If possible, avoid using pull-ups. It has been my experience that forgoing the convenience is far worth the trouble. Children who feel the comfortand dryness of a pull-up do not potty train as quickly; for they are not able to feel wet. Thus, it is easier for them to make the appropriate association if you use underwear.   
I have worked with young children since 1986, and have helped several families through this process. Therefore, I must add one final bit of advice; never disciplined a child for having accidents. The process may be difficult at times, but always focus on the positive.

Time to Pee! Mo Williems
The Potty Train David Hochman
Toilet Tales Andrea Wayne
On Your Potty Virginia Miller
Caillou Potty Time Joceline Sanschagrin
Ruby's Potty Paul & Emma Rogers
Standing Up Marie-Anne Gillet