1.
Constant communication -- Call each other as often as possible.
By sharing what is going on in each of your lives you can stay close emotionally.
Don't wait until you have some big news to tell him.
Give him a call even if it's just about mundane things, it will help keep your relationship together.
2.
Use instant messaging, text messaging, or email to communicate.
This is especially useful if you have to worry about long distance charges.
You can also email or send each other text messages all day if you like.
3.
Plan vacations together when possible.
If you can both get time off around the same time, use it for a romantic getaway.
4.
If there is a place about halfway between the two of you that is within a few hours driving distance, meet there once a month on a weekend.
Rent a hotel room for the night (or two, if possible) and spend as much time together as you can.
5.
Send each other hand-written notes and little gifts.
It is not a great substitute for seeing each other, but a real, hand-written letter is something tangible that you can touch and re-read as often as you want.
6.
Send each other pictures as often as possible.
Show him that new dress you bought, or even let him see the new pillows you bought for the sofa.
Do everything you can to keep each other updated on your lives.
7.
Get a web cam and chat with each other as often as you can.
Getting to see him, even if it is just on a computer screen, can help with those lonely feelings.