addendum
Techniques you've probably already tried but are still worth trying again.

See a Doctor
Take a Warm Bath
Get a Massage
Listen to Music
Drink Warm Milk
Drink Herb Tea
Eat a Bedtime Snack
Avoid Caffeine, Alcohol and Tobacco
Sleep in a Well-Ventilated Room
Sleep on a Good Firm Bed
Sleep on Your Back
Get Some Physical Exercise During the Day
Keep Regular Bedtime Hours
If You Can't Sleep, Get Up
Don't Sleep In
Get Up Earlier in the Morning
Keep Your Bed a Place for Sleep
Avoid Naps
Avoid Illuminated Bedroom Clocks
Of course there's the standard technique that everyone knows (although it never worked for us)
Counting Sheep
And some techniques you probably haven't seen before

Sleep With Your Head Facing North
Don't Watch TV or Read Before Going to Bed
Toe Wiggling
Stomach Rub
Progressive Relaxation
Deep Breathing
Visualize Something Peaceful
Visualize Something Boring
Imagine It's Time to Get Up
Quiet Ears