I have a BA in environmental science, a MS in geochemistry, am currently doing a MS in applied math, and will be starting a PhD in geography in the fall. This looks more scattered than it really is--everything except the math degree is all the same sort of research, it's just that what I do doesn't fit into one department very well so where I end up depends on the school.
As far as tips go, when I was applying for the math MS I talked to the program director and explained that while I didn't have all the pre reqs, I had a variety of related academic experience that I thought would prepare me adequately. I'm pretty sure that if I hadn't communicated with him before submitting my application he probably wouldn't have considered letting me in. I also spent a fair bit of my personal statement explaining how this degree fit with my prior experience and what I planned to do in the future, so it looked less like I was randomly switching departments for a year. (And when I was applying to PhD programs in my usual field, I again made sure to justify this year of doing math and fit it into my overall career plan.)