When you ask for email, it's very low risk for a woman,
so she'll think "Fine, I'll do that." Most women will give out
an email address without thinking about it, because they know
that they can choose later to just not answer.

The magic of asking them to write their phone number down
WHILE they're in the middle of writing down their email is
all about the psychology of human behavior.

She's already mentally said "OK, I'll give you my email
address"... and she's in the middle of writing it down. When
you say "And just write your number down there too" it's only
NATURAL to just write it.

In other words, it's a MUCH smaller step than giving out
the phone number all by itself. It took me a LONG time to
figure out this simple move, but it works like magic! You
will have women writing their phone numbers down without even
thinking twice.

Here's a great add-on to make sure you're getting a real
phone number and not a pager or voicemail:

As she's writing down her phone number I say "Is this a
number that you actually answer?" If she looks at me and
hesitates, or says that it's her "voicemail or pager number,"
then I say "Look, write your real number down. It's going to
be OK, I'll only call you nine times a day..." They laugh
and usually give me their real number.

Now, if she answers my first question and says "No, I
don't have email" then I bust on them and say "Well, do you
have electricity?" This is a GREAT opportunity to use humor.