One of the thing that seems to help with mild insomnia... not as much with pervasive cases. Is to begin following a nightly sleep ritual. Basically about 1-1/2 hours before you want to be asleep begin to dim or turn off lights, get ready for bed (brush teeth, etc,) and find a relaxing activity to do in bed (reading, etc.). The body is naturally tuned to respond to lower light and if you are able to relax in that environment it helps to ease people into sleep.
Other things are to stay away from naps, caffeine (espeically close to bed time) and try to work into a regular (getting up and going to bed at the same time) sleep schedule. If those things don't work then its a good idea to meet with a physician or counselor to see what other options might be out there.