A single abnormal cervical smear result is a relatively common occurrence, and for much of the time are not cause for concern (About 75% of low-grade abnormal smears revert to normal given time). What sometimes causes confusion is that smear results can come back as 'unsatisfactory' (the smear is unreadable), usually because of an infection - and a repeat is required in a few weeks: note that unsatisfactory does not mean abnormal.
After a single abnormal smear result, you should have an appointment for a repeat smear in a few weeks. If this is normal, then no follow-up over and above routine smears is required.
If smears are repeatedly abnormal, or if the initial smear is very abnormal, then referral should be made for 'colposcopy' (a procedure done by a gynaecologist at a hospital or clinic, which involves examining the cervix with a microscope). In some cases, a biopsy (taking of a tissue sample) can be done at the same time using local anaesthetic - this is the gold standard and provides definitve diagnosis.