Three Sisters Planting?

Hi All,
I think we've seen our last frost (just got a big snow storm last weekend, but it's looking like Spring now.), and I'm ready to begin planting... This year I'm using the three sisters planting method (corn, beans and squash) for much of my garden space. I'm wondering if anyone has any helpful hints or tips to share. Watering methods? Soil boosters? Special companion crops? Favorite variety?

Any information is much appreciated.
Many thanks,
Julie