1.Write. This may sound simplistic, but the best way to learn something is to actually do it. That applies to writing too.
2. Read. I've heard people say they don't read while they're working on a novel because they worry that their own voice will become corrupted by it. I think this is nonsense. First of all, no one can create in a vacuum, and secondly, why deny yourself the kind of pleasure you're hoping to give to others one day, with your book?
3. Set yourself realistic targets and finish what you start. That's exactly what you'll have to do once you have a contract, so you might as well practice now.
4. Find a writing buddy or a support network. No one except a fellow writer truly understands what it's like to have your work rejected, and this kind of support is vital to keep you going.
5. Don't try to be something you're not. If you write, say, light-hearted chick-lit, don't impose a literary style on it. It won't work. Instead always be proud of what you do, whatever your genre or niche
You can read Jenni's review of Henriette's book, Up Close here.