See dentist/orthodon. You cannot change how teeth erupt, but you can get a plan at an early age. Most good orthodontists will see children in consultation at age 4-8 years. They may not do anything at that time, but they may need to start a plan early. Depending on the nature of "crooked" (crowding, etc.) you can begin to develop a plan to minimize the problem and speed the correction. Good ortho's do consults free.
Creoles teeth. Unfortunately not. There are things we can do to give teeth more room to erupt but this will not prevent them from being crooked. Teeth have a mind of their own and if they want to grow in twisted or rotated they will. Nonetheless, an early consult by age of 7 with an orthodontist could prevent a lot of issues from getting worst. Go to www.Braces.Org for more info.
Not Much, But... Much of the dental "look" is genetic, but stopping bottles and pacifiers at 12-15months of age clearly helps minimize dental problems. Also trying to divert thumbsucking soothing to other comfort objects such as a stuffed toy helps.
Depends. You're not going to change your child's genetic eruption pattern, but you can make sure baby teeth are healthy, and have space maintainer done if any lost prematurely. You can discourage pernicious digit habits. You can promote healthy diet to prevent cavities resulting in space loss. See and orthodontist at age 7. Sometimes arches can be developed to provide additional room.
Not much. Regular dental check ups to have a healthy mouth. Wait and watch. Your orthodontist can give an idea of the future alignment of your child's teeth.