Dear David,
Well, there are many paths to becoming a scientist, but a very important skill is mathematics. So, take a lot of math, and do that early. You should be in algebra by grade 8th if you can, but definitely by grade 9th. Take 4 years of math and science in high school. Go to science museums and have fun with science. Go outside and observe nature, carefully, taking your time. And don't forget to enjoy nature, be part of it! The Universe has much to teach us all. Hard work is also good for any career, and being able to communicate well, and generally be a nice person so you can work in teams, since science these days requires people to work in groups.
Isabel