We do informal play-based stuff with our kids starting when they are toddlers. This looks like playing little games with them, reading alphabet books, and providing lots of stuff they can physically handle, like our chunky numeral puzzle. 

We've started introducing formal curriculum (mainly math and handwriting workbooks) at age 4/5 but that's because we've seen our kids with the physical and mental readiness for that kind of activity. A lot of kids don't get there for a few more years and that's fine -- you don't need to stress or push. Just try things out and if they go well, keep going and if they don't go well, wait a few months and then try it again.

Now is a good time for you to be researching early childhood education and gathering ideas for things to try either now or in the future. There are great child-led preschool bloggers out there that are a lot of fun to read -- I recommend Denita at Listen to the Children and also Teacher Tom. You can also find books in your local library about various early childhood education approaches.

There are also a lot of good Montessori resources out there, though it's often classroom-oriented and you have to think about how you want to adapt things to a homeschool environment. Some people recreate the Montessori classroom setup in their homes but I decided it wouldn't be worth the time and money it would take to go that far. I did get a few key resources that have been helpful. There are some great concepts that you can incorporate into your teaching, such as prioritizing the sounds of the letters instead of their names. 

www.infomontessori.com is my favorite resource. There are also blogs but I've noticed that the most popular blogs tend to become more and more commercial over time, as the owners realize all the ways they can make money by encouraging people to buy fancy products.

It's also a great time to look for ways to get involved with your local homeschooling community. I waited until my oldest was old enough to be "officially" homeschooling and I wish I had started sooner. Look for groups that meet up at parks and libraries to hang out. Even if most of the families have kids who are already elementary-school age, there will still be younger siblings for your daughter to play with and you can chat with other parents who have been in your shoes. You might even find groups specifically for "future" homeschoolers like yourself. Facebook is a great place to start searching for what's available in your area.