What's your cooking style? Your primary kitchen knife should be suitable for the jobs you do most often. For precision work, such as cutting paper-thin slices of carrot or potato, many chefs find a light, straight-bladed santoku knife the ideal tool. For mincing, by contrast, most prefer a traditional chef's knife, which has a curved blade that rocks smoothly up and down as you slice.
Are you prepared for long-term knife care? Experienced cooks agree that a high-quality knife requires regular maintenance. It should be washed by hand, dried promptly and stored securely. It will also need regular honing with a sharpening steel to maintain its edge. If you know, realistically, that you won't do these chores, then you may prefer a low-maintenance knife with a dishwasher-safe handle and a corrosion-resistant blade. Some knives also boast that they will hold their edge without sharpening, although that edge most likely won't be as keen to start with.
To find a knife that fits your hands and your chopping style, you need to test it in person. Find a store with hands-on demonstrations for a variety of knives that you can hold or, better yet, practice with on a cutting surface. The handle grip should feel secure, and the blade should be wide enough to keep your knuckles from bashing into the cutting board. You will also want a weight that is comfortable for you.