Summarize:

It may not always be possible to do this, but it is important to limit their exposure as much as possible.  If you do not live in an area with laws banning smoking in restaurants, look for those that voluntarily ban smoking. Avoid theaters, entertainment venues, and anywhere that smokers are likely to feel comfortable lighting up. Be aware that even in places where smoking is banned indoors, many places still permit smoking on outdoor patios. Keep your children away from the tables of smokers or take them indoors. If you must be near the person smoking, kindly ask them if they could refrain while your children are present.  Explain to the smoker that you only wish to protect your children’s health. However, be aware that they may refuse. Be understanding of their choice, if they refuse to stop smoking. This might be hard, but do your best. Be prepared to remove your children from the smoking environment, if necessary. You may have friends and family who are not ready or are unwilling to quit. You should take the time to explain to them that you value their presence in your life and your children’s lives, but that you cannot allow them to smoke around your children, and that your children will not be allowed to be around them while they are smoking. Help them understand how they are putting everyone around them at risk when they smoke, particularly children, who are still developing. Do your best to be firm, but also respectful. If your child wants to have a sleepover at a friend’s house, but you know that the parents are smokers (especially if they smoke indoors), do not allow them to go. Suggest instead that your child’s friend comes to your home for a sleepover.
Keep children away from public places where smoking is concentrated. Remove your children from areas where people are smoking. Forbid friends and family from spending time around your children while smoking. Avoid the homes of friends and family who are smokers.