Scouting is key. Scout the place, check when the not so busy hours are or the not so busy days.
Check out the DJs and what they do and compare yourself to them, to know what key features you can bring compared to them.
Getting in touch with managers is different so scout. Some roam their venue and you can easily ask a waiter that you would like to talk to them. In some cases they like to be approached by phone or email to get an appointment.
In the talks stay calm, state what you want to do, what you can bring and your salary. The salary is non-negotiable (at least this is what I do).
Will you get rejected?
Yes. A very good turnaround is that in 30% of the cases you get somewhere, when you are starting out that is. Some begin with a turnaround of 10% or less, depending of the region you live. So do not get frustrated and keep at it.
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