You Can Build Better Self-Esteem
Healthy self-esteem is vital to a person's person's personal and professional success as well as their social happiness. People that like themselves are more likely to present themselves to others as someone that is likable. They have stronger belief in their abilities, are less afraid to take personal and professional risks, and are more able to cope with life's failures.

Self-confidence can be strengthened in people lacking it but it takes concious effort over time.
Keeping goals realistic will help with one's self-confidence. Unrealistic goals that are impossible to meet only set one up for failure while realistic goals will set one up for success. Each consecutive success will help foster that budding sense of self-confidence in a person. They will eventually learn to believe in their own abilities instead of expect failure. This belief in one's abilities is key to healthy self-esteem.
Avoid being overly critical of one's self. Failure happens to everyone. Viewing mistakes as opportunities to learn instead of horrible and predictable results is vital to a healthy self-esteem. It is equally important for one's self-image to not be overly critical about one's looks and traits. Learning to accept that everyone has things that they do not like about themselves but seeing that they have admirable qualities is important o healthy self-image and healthy self-confidence.
Changing what one does not like about themselves if it is realistically able to be changed will help with both self-confidence and self-image. If one is not happy with their level of education take classes to improve that. If one does not feel that they have adequate skills then find training in order to improve that. If one thinks that they are too heavy or too thin then seek the guidance of a medial professional and change that in healthy, realistic way. Understanding that while some things such as height cannot be changed but some things 'can' is vital.
Self-esteem is something that can be fostered and improved over time with effort. Taking these simple steps will put a person on the right track but they are far from the only factors at play in this complex trait. Everyone will suffer from moments lacking confidence in themselves and everyone will need to rebuild their levels at some time or another.
Understand that this is a natural part of living and accept it as just another challenge to overcome.