There are four conditions for wrong conduct in sexual pleasures.
- There must be a man or woman with whom it is improper to
have sexual intercourse.
- There must be intention to have sexual intercourse with such a
- Action must be taken to have such an intercourse.
- There must be enjoyment from contact of the sexual organs.
With reference to the first condition, there are twenty kinds of
women with whom men should have no sexual relations. They can
be divided into three groups, namely:
- women under the
guardianship of parents, family members, relatives and authorities
charged with their care;
- married or betrothed women;
- bhikkhunis and religious women observing the Holy Life.
For all women,
- a man forbidden by tradition or
- under religious rules
is prohibited as a partner.
If someone is an unwilling partner, who is drugged or forced to
have sexual intercourse under threat of violence or coercion,
conditions (2) and (4) exclude them from having violated the precept.
Source: FIVE PRECEPTS (PACASILA) - urbandharma.org
It is also sexual misconduct when one engages a partner at an inappropriate time, such as when a woman is pregnant, or when she is nursing. It is unethical to take the mother away from the baby for sex. It is also misconduct to have sex at inappropriate places, such as at places of worship.
Source: The Third Precept: Abstain from Sexual Misconduct
Also it is sometimes considered Poya / Uposatha is in appropriate time to have sex.
In addition, outside the bedroom is considered an inappropriate place in some interpretations.
As for the question about fornication: if the partner belongs to a category you should not have sex with, then you break the precept.