A DJ should have his crates set up from his past experience with DJing parties & weddings, but if the Bride & Groom or client have requests, then definitely he/she should use those songs in addition to his own.
It should always be the DJ. I understand if the client has a list of songs to play through out the night but, thats the DJ's job to mix them in with his sets.
If it’s a wedding you have to make the bride and groom happy because they will remember this day for the rest of there life and you gotta keep the floor full,it’s hard being a mobile DJ especially for coolie people they make you earn your money.
I agree you are hired to full fill there night of memory and fun. If a list is given always work it into the mix. I alway meet with the clients 1 month before for songs request and finalize one week before. This way I can place them in to my set so I covered all their requested songs.
First, it depends on the event. If it’s bars or lounges, it’s up to the DJ and they should control the music. But if it’s weddings, I personally think that both the clients and the DJ should do the music because the bride & groom would have requests to play (like MrInfamous Vibes and DJ Chucky said), but other than that, it’s the DJ all the way.
You should have your core crate for the event and add any additional songs that the client request if it's not already in your list.
