When you trust the person enough to exchange numbers, then it is advisable to give them out.
Also, when meeting for the first time, choose public locations for the first couple of weeks.
Be honest about what kind of partner you're looking for, and what preferences you'd like him/her to embody.
In this way you can attract those who are of similar backgrounds, and can be assured that they will fit your criteria.
Make sure you also have your age displayed, to avoid an age group that you aren't comfortable with; do not lie about your age.