Be prepared for the boy to feel hurt and rejected.
Even if you've gone together for only a short time,
and haven't been too serious,
there is still a feeling of rejection
when someone says she prefers the company of others
to your exclusive company.
But if you are honest and direct
and avoid making a flowery emotional speech when you break the news
the boy will respect you for your frankness
and honestly, he'll appreciate the kind and straightforward manor
in which you told him your decision.
Unless he is a real jerk or a crybaby, your gonna be friends.