Tip 1: Be consistent
Transforming your body takes time. Being consistent with proper training and nutrition is the key to seeing muscle definition. Find a program, be consistent, and you will see results.
Tip 2: Compound movements are your friend.
Yes, crunches are alright but doing full body compound movements such as squats or dead lifts should be a staple in your training program. These full body exercises will develop overall muscle which will make your overall body composition better which means you will have more muscle definition. Remember there is no such thing as spot reduction.
Tip 3: H2O
Drink water!! A lot! The more water you drink the less water you hold.