No matter what type of "approach" you do-
The key to getting phone numbers is- ASKING.Background
Yesterday, July 9th, I walked up to 17 girls at the mall and asked each of them for their phone numbers.
Other than "Hi.", "Can I Get Your Number?" was basically the first thing I said, often in about 10-15 seconds.
In most cases, I introduced myself right after and reached out and shook/took their hand.