My two boys are 15 mos, 10 days apart. I don't have any magic tips for you, except to get help from family or friends if at all possible. At the time that my second baby was born, my husband (military) was working very long hours (as usual) and was not able to take any time off - but fortunately the baby was born on the first day of a 4 day weekend for him :). We were living some distance away from "home," but I had several family members take turns and come stay with me for a few days each to help during the first month. I don't know how I would have survived without their help! After the first month, I was on my own, but I adjusted to handling two babies alone after another month or so.
It is not easy, there is no way around that, but I would like to share some of the wonderful aspects of having two babies so close together. My oldest son adores his little brother (and vice versa). I was fortunate to have my babies at home, and my oldest was in his room with his grandparents when his little brother first "arrived" in the room down the hall (don't worry, he was not a witness to the birth!:). His grandparents had just put him to bed when they heard the new baby cry out, so they got him up and he got to meet his new little brother within the first few minutes of his birth. My oldest was a little bit bewildered - no matter how much I talked to him about the new baby coming and the baby in my tummy, I don't think he had a clue. But I think I will always remember that moment when my boys met each other. My oldest just wanted to play with the baby, which hasn't changed. And he gave the baby kisses and wanted to "nuzzle" with him, which has continued to this day also (they are 3-3/4 and 2-1/2 now).
The first year or so was tough training ground to get my oldest to learn that he needed to be gentle and careful with his little brother. I had to watch them constantly - not because he would hurt the baby intentionally, but only because he didn't understand yet that his playfullness could hurt the baby. I got an extra playpen to keep in the living room so I could put the baby in there if I needed to step out of the room for a moment. For the first 1/2 year or so, I couldn't leave the baby on the floor and look away for a moment if big brother was in the room.
My oldest son is very nurturing and has always tried to help me take care of his little brother. I'm sure you will have this with your daughter, too, because girls are usually naturally that way. As they have gotten older, my oldest really can help me with things, almost just in time for the little one to learn to do things himself! :)
Another benefit of having them so close together is not having to deal with jealousy, from what I have experienced. Sure we have some squawbles over toys and they do their fair share of trying the "mine" game (which doesn't get them very far in our house) but I can't say that I have ever seen anything that looks like jealousy (of course, the day may still be coming). We make a great deal of effort to give lots of affection, praise and encouragement to each boy. I come from a family of 7 children and my mom was a single working mom for many of my younger years, so I know I didn't get a lot of "attention" or time with my mom, but one thing I do know for sure (and have always known to my recollection) is that she loves each one of us unconditionally and there is not one of us who has ever been more favored than another - my mom has always said that each one of us is her favorite, and I believe her!
One other bit of advice is that having a daily routine was very helpful for us. We attempted a routine from birth for both babies, and by the time they were about 3 months old, they were nicely settled into a routine which gradually changed as they got older. This was a life-saver for me once we had two babies. My first baby dropped the morning nap right around the time his little brother was born, but I was able to get them on overlapping afternoon nap times by the time the second baby was a few months old, then after another few months they had the same afternoon nap time. Once the new baby was established in his routine, his morning nap time was a nice, quiet time for me and my older son to have some time together. They still take the afternoon nap at the same time(though my oldest will often only "rest" in his bed and not actually sleep) and that little break in the afternoon is most welcome and needed!
From what I have read and what I have experienced first-hand, routine is very helpful for children. They have a sense of security that comes not only from loving parents, but from predictability in their day. If you don't already do this and would like any tips about getting them on a "schedule," let me know and I can either give you my own version or refer you to some resources that I followed.
Overall, you are in for a wonderful experience. I often get stressed beyond belief, but I have two amazing little boys who love each other. It is a really tough job as a parent, but my boys are so happy to have each other, and I am glad that I was able to give each one of them the gift of their sibling. I'm still living in the midst of some difficult days (just wait till you have two of them throwing tantrums!) but I know that when they are grown, I will most likely look back fondly on these days, and I won't regret a moment of it.
Congratulations and best wishes to you! Oh, and if you need any help looking for a double stroller, I can share my double stroller journey with you. :)