The proper way to request songs or actions by a DJ is still not completely understood by the general public but it's not because we're doing something wrong. The reason is that the general public just thinks a DJ is there to serve, end of story. But it depends on the situation.
Many people experience a DJ at a wedding for a friend or family member. In that case, the DJ is usually paid for any occurrence that might pop-up such as an impromptu singer or an endless line of requests for obscure songs. But when a DJ works at a club or restaurant, chances are that DJ is being paid a lot less than an event like a wedding. They are being paid to simply "play music." And when people walk up and ask for a song or two it's no problem. But, when multiple people are requesting multiple songs and sometimes even with specific instructions of when and how to play the request, slip me a tip. Why? Because I've planned a set and now you've decided that you're going to make an executive decision and change the flow. Should a chef allow restaurant patrons to make changes to his or her ingredients and menu? NO! Apart from that, I am paying for everything (Including the music itself) so every little bit helps.
I have recently had to resort to letting people know that my being a DJ is a part of my living and that if you're coming to enjoy what I've planned then fine no charge. But, don't order me around and not give me a lousy dollar or two!