The best way to prepare any child for learning and for life is to read to her. Read regularly, read with expression and delight, read fascinating stories, read a wide range of stories. You would be amazed at the pile of books it would be that we have read out loud to our children - the longest being The Lord of the Rings.
The second important thing is to give her imaginative, hands-on play, especially outdoors. Building forts or fairy houses, dressing up in period costume, (maybe not when she's this little) doing interesting things with hands and dirt and objects, climbing trees. Always minimize electronics and media. Some television is not bad, but it's not that good, either.
And third, as she gets older, give her broad experience. Make it normal to go see a Shakespeare stage presentation or a period costume foray such as Dicken's on the Strand at Galveston (we have gone all dressed up, it was so enjoyable), or any of a number of such things. Give her a broad experience of the world and culture. Kids who grow up surrounded by other kids their own age (modern education) will despise all these things by the time they are teenagers - that is the de-socialization that takes place in the modern classroom.
And keep your daughter away from such continuous environments. Playing and learning with other children is always good, but not the endless hours that modern education demands. You want social experiences for your daughter? Invite another homeschool-minded mother of a child your daughter's age to your home and let them play together while you watch and visit.
Then, there is no reason to rush formal education. It would be better if a girl did not begin until age 7, and a boy until age 8, unless they ask you to teach them to read (which they very well may do, quite out of the blue). A child, especially a boy, who starts later, will almost always catch up with those his age who started early in just a short time and surpass them. Learning is now easy for him, and he has no reason to hate it. Forcing kids to learn things they are not ready for because that's what "the program requires" is the creator of the most powerful lesson I saw learned in the public school. It is an almost universally successful learning outcome - learning is to be despised.
There are some sound principles inside the "unschooling" philosophy. I also know the value of discipline in learning, but both - guiding by interest and requiring discipline when it counts - are important.
Finally, when you do teach your daughter to read, and this should be a joy that all mothers share, then I recommend "The Writing Road to Reading." It is a sound program, based on reality. My wife used it with great success, with others as well as our own children. Around the time you see your daughter puzzling over the words in books, having discovered that they mean something and curious what it is they mean, get "The Writing to Reading" package from website
Learn the system yourself, first, then, when she sees you working with the sounds (somewhere between ages 5 -7) and asks "What's that, Mommy?" you know she is ready for school.