I was in a similar situation for about six months. (I was the one temporarily in another part of the country.)
It is hard. For both of you. Acknowledge that often.
Make a set time to talk every day. DO NOT let anything going on in your social life interfere with that. Not even once. If you agree to talk at 6PM or 10PM or whatever, make sure that you are alone in a quiet room to do that.
Find a way to get her a night or afternoon to herself on at least a weekly basis. If it means cutting back on something to hire a babysitter or calling in favors with friends or whatever.
If you haven't already done so, make arrangements for her to join you for at least a weekend. Even if it was for good reason and she understands that on a rational level, part of her has to feel left out. Introduce her to some of your friends, and take her to a bar or restaurant you frequent. Let her feel like you aren't excluding her from this part of your life.
And this was a big one for our relationship-- stay very positive about your work situation. Even if you have something legitimate you need to vent about, be careful to not say many if any negative things about work. You don't want to ever give the idea that you are choosing a bad job over being with her. (My husband eventually started saying that to me when I complained about my boss for the tenth or so day in a row. Even if it wasn't logical or rational, he was interpreting that I was choosing a bad situation over my family.)