If you have a photographic memory, screen the regulars and filter out the random guests. Don't waste time on the random guests.
When you see a regular or a group of regulars coming over, sarge them for 2 to 3 minutes each and eject. The bail out or ejection is key so you can build trust. You don't want to come off as having vested interests like getting them to invest in your business or something.
After 3 or 4 encounters, casually ask for their numbers if they have not asked for your number yet. Once you build trust, they will usually be the first ones to ask for your number.
Where I'm Coming From
As a consultant for an engineering firm a few years back, part of my work involved taking out clients and business partners to clubs. We wine and dine these people. We all get girls every time. All expenses were paid by the corporation.
The unfortunate thing was, no bouncers ever built rapport with us. Floor managers usually did this job but they never took it to the next level where we can hang out during the day or after business hours. But the club girls were fairly good at this if you gave them enough fun. We hang out with some club girls at the beach and other venues during their leisure times.
The waiters too were good at this. In fact, some of my friends and clients invested in some business that a waiter offered. The waiter built solid trust with the non-needy approach I described above and by providing good, even excellent, service. We always gave him a tip every time.
Hope this insight helps.

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Approach. Open. Escalate. Isolate
Here are my two essential rules on texting that will save you tons of time and money:
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