There are different ways to try to work with restlessness before trying to fall asleep. Steve has recommended that we do some Compassion/Lovingkindness meditation before going to sleep. Usually I recommend trying to focus on the lovingkindness side more than the compassion side, as thinking about Dukkha too much can make you more restless. Focusing more on the repeating of the phrases, as well as using shorter phrases can help to calm the mind down.
Something else I have done when I've had jet lag am finding it difficult to fall asleep, is to just watch the arising of the thought but not allow it to finish, like bubbles. Sometimes we are trying not to think, and trying so hard on our meditation subject can generate more energy in the mind. This is not actually very helpful for falling asleep. So just using bare awareness has been very helpful, observing the arising of the thought but not following it and not allowing it to end, has been very helpful in those situations so that we are not bringing up too much effort at those times.
With certain types of people, watching the breathing can brighten the mind so you have to try to understand what type of person you are. Learning how to relax the body while we are lying there. Sometimes if we have restlessness we may be holding the body tense and not even realizing it.
One of the things is to check whether you are worried about not falling asleep. Oftentimes the worry and the fear about not falling asleep, "I'm going to be exhausted tomorrow!"--creates a lot of restlessness so you can't fall asleep. So checking to make sure you are not projecting a limited idea of yourself at that time is very helpful. If there tends to be a lot of doubt arising there, to remind yourself of a time when you didn't have much sleep and you were fine the next day. Because often you may have one night of not so much sleep and the next night you make up for it, so not projecting a limited idea of ourselves for the next day is very helpful for calming the mind down. This is where confidence-inspiring objects can be very helpful. Sometimes when I'm jetlagged I have some of the nicest meditations in the middle of the night. So seeing it as an opportunity and not as a problem.