Set up a schedule

Kids need consistency. If they have a nightly routine they will know that bedtime is approaching--it won't be a surprise. Here is a sample.
-bath time 7:15 pm
-snack or small drink 7:30 pm
-brush teeth 7:40 pm
-story time 7:45 pm
-family prayer 7:55 pm
-bedtime 8 pm

Be firm

-Kids try to push the limits. They'll try to get away with all that they can. If they know that they can get out of bed a couple of times a night with no punishment, they will. Be firm. Once they're in bed, they're in bed for the night.

Play quiet bedtime music\

-Sometimes "quiet noise" like soft music, a fan, or a humidifier will be music to your child's ears and help them fall asleep fast. If you try music, make sure to keep the tempo slow and soothing. Earphones might even be appropriate for an older child. (Note, make sure the cord doesn't entangle him/her.) 

Offer "Personal" Stories

-Kids love to hear are little. Tell them stories about themselves when they were little or stories about yourself. This will provide good memories for them and also help promote your family history and stories.

Tire out your kids

-Make sure you keep your kids active throughout the day so that they are tired and ready for bed. Physical activities help give your kids the exercise they need and get out their energy. Make sure that activities slow down, however, at least 2 hours before bedtime. You don't want to get them too energized and not ready for bed.

Start young

-It's best to start these rituals and habits while your children are very young. Kids are more flexible at younger ages, and will learn your bedtime routine. Starting a routine later in their life is possible, but will be harder to teach them. If they're used to getting up 50 times after you put them down for the night,  then implementing a "no getting up after you're in bed" rule will be difficult to grow accustom to.

Nanci Hellmich, "Routines are key to little one's dreamy nights" USA Today, March 24, 1999