If you're working with a point and shoot, switch to macro setting and get close to your food, press half way down so it focuses (put your camera on auto focus) and you will see a sharp point of focus amidst a soft blur. This compositional device allows viewers to dive into the specific, tasty area of the photo. Some folks use this aesthetic all the time, others infrequently, others never — it's totally up to you.
2) Choosing the Right Lens. A lot of photographers will weigh in with different answers to this question. For me, I believe there is no "perfect" food lens. Shoot with what you've got. I shot some perfectly gorgeous food photos (and photos of other things for that matter) with the kit lens my first DSLR came with. It's not the lens, it's the person behind it and knowing when your light is soft and pretty. Having beautiful light paint itself across the food is more critical than a specific lens. That being said, a lot of phtoographers love to shoot with prime, fixed lenses. So think about a 50 mm 1.2 or 50 mm 1.4. I shoot primarily with a 24-70mm telephoto lens, and I love it, so go figure!
3) Work with Others. If you can involve strong home chefs, people who understand plating food and care about what's being presented, you can improve your food photography. You can learn from the way they do things. I work with a professional chef, my good friend and colleague Adrian Hale, whenever possible. She knows how to put the grill marks on the steak just right and she even peels carrots, something I'd never do. This allows me to focus on the flow of the image and not worry so much about the food. Working with friends also makes life more fun and less work when you can share the dishes.