Patience

Patience is your friend and it is a skill you had better
master. Once you've located a potential mark or asset. You'll want
to take your time before making contact. If you appear too eager
they will know your up to something. Don't act disinterested,
just indifferent, or mildly interested but slightly distracted.
After an initial contact, you will have to casually make a second.
But wait before you do so. Plan and wait. Do your research and if
the situation calls for it, surveillance.
A casual email about something they find interesting might
get their attention. Do not be obvious. The email should contain
only a hint of what interests them.
The key is that they contact you back. Then begins a dialog.
But wait. Don't respond too quickly. In some cases it might make
sense to wait months between contacts. Remember. Learn to lie and
learn patience.