First, try not to make any changes in your daughter's life for the first 6 months or so.  This includes potty training, room reassignments, day care changes, etc.  She will be coping with a ton of change just by your adding a new baby, try not to add more. 

Also, remember that she is still a baby, too.  Make a conscious effort to sit and hold her, play with her, and talk to her often.  It's easy to get wrapped up in the new baby, but try to spend special time with her when the baby is napping and when daddy is home.

Lastly, cut corners where you can in house keeping.  Your house will look a bit rough for the first 6 months or so, but that's to be expected.  I tend to simplify by using paper plates and cups to decrease the frequency that I have to do dishes.  I also prioritize cleaning.  I keep the main part of the house presentable at all times, but only get to bedrooms when I have a chance in the early days.  In 20 years it won't matter if your house was spotless, but it will matter to your daughter that you took the time to come to her tea party, despite the messy bathroom.  :)

Good luck and remember that this will be a hard time for your little girl.  Try to look at why she is doing the annoying things she will do from the perspective of a 2 yo, and go easy on her.  :)

My kids will be 25 months apart.. I'm a little nervous about that but I'm hoping that we can all easily adapt.. I try to get my son used to the idea that I am having a baby but its hard to know if they really understand it.. Like he will kiss my tummy and say baby but does he actually know? I dunno..

see machaela does that too she seems like she knows...i wander that too???I got her a baby doll n we chnger her diaper and feed her n put her to sleep so maybe it will help

Levi likes to play with his baby dolls.. He also will see a baby and say baby.. So he knows what a baby is. Its just hard to understand if they actually know that you are gonna have a baby..

My kids are 2001, 2003, 2005, 2007 and now 2009. My middle are 16 mo apart. Changes are hard on them, ease into it slowly. Believe it or not, they will be best friends one day!

My son and the new baby to come will be 26 months apart. But Tre is a very independent person and loves to play, i dont think it will be that hard, but definately a change to adjust to. He is a very good helper too. He has a baby doll to play with and even puts in his old carseat and rocks it. =) he will be a good big brother!