If someone has the nerve to wave me down at the bar, then I expect them to be ready to order as soon as I approach them. I don't know how many times a night I get waved down by an impatient customer only to have to wait for them to have a discussion amongst themselves about what they want to drink. When this happens, I give said impatient customer a short amount of time before I move on to the next customer.
If I see someone come up to the bar with cash in hand, ready to order, you bet your ass I am leaving the impatient customer momentarily to help the customer who is actually ready to order and pay.
Don't wave me down unless you are truly ready to order and pay or else I will leave you for someone who is. Wavers end up waiting longer for their drinks than usual because they are so impatient.
Be patient and be ready. You'll get faster and friendly service, guaranteed.