Establishing a diagnosis involves examination, review of medical and dental history, clinical data analysis, and tests that are specific to your condition. Only a dentist can evaluate your signs and symptoms to establish a diagnosis.
Chipped anterior teeth (the front ones), which are visible in the smile, are nearly always reported by the patient to the dentist on an "urgent—need to be seen" basis. Many patients are unaware of chipped posterior teeth (the back ones).
The dentist's challenge (especially with anterior teeth) is to rule out more significant problems, like a serious head or neck injury that may have occurred at the time the tooth was chipped. He or she will review the events that caused the chip with the patient or patient's parent/guardian. If there is a possible mechanism for a more significant injury (e.g. child hit the dashboard in a car accident), or if abuse is suspected, the patient will often be referred for further evaluation before dental care is provided.
When the patient is cleared for dental treatment, attention is turned to diagnosing the severity of the chip. If the pulp (nerve and blood vessel tissue) is exposed, the tooth will generally require endodontic (root canal) treatment before a final restoration to the tooth is done.
Learn more: Procedures › Endodontic treatment
Many times a chip is a blessing in disguise, in that the forceful blow to the tooth is dissipated in chipping the tooth (in much the same way as a bicycle helmet is designed to come apart in an accident, and prevent the victim's head from absorbing the shock). If instead, the energy is transferred into the root of the tooth, the fragile nerve and blood vessels may be severed, and the tooth can abscess, requiring more extensive treatment.
If a large portion of the tooth's crown (the part you can see protruding through the gums) has been lost, the dentist may recommend that a structural post be placed into the tooth's root canal, and then build the crown of the tooth around it. This would necessitate endodontic (root canal) treatment before the post can be placed. However, modern bonding materials have again pushed the envelope of what is treatable without a structural post to new heights:

Figure 1a: A more involved anterior tooth chip. About half of this tooth was chipped away in a street hockey accident. The chip narrowly avoided exposing the tooth's pulp (blood vessels and nerve).

Figure 1b: Bonding was performed on the tooth shown in the previous photograph. At the time of this photograph, it had been in place for six years without signs of failure. The tooth remained vital (i.e. "alive") and was asymptomatic. Use of an athletic mouthguard was encouraged for this active young boy.