First of all get our wedding DJ guide. It will open your eyes and the playlists alone are worth the money.
As for the songs a couple requests. Talk to them, make THEM think about the guests they invited with questions like “is your granny present and do you think she likes Megadeath too?”.
Ask them in terms of themes for specific parts of the evening:
Like “music during dinner”, “music as long as elderly are present” and “party music for the late night dance”. Special dances like first dance, father daughter dance, brides dance,…
If you DJ also during the ceremonry ask the couple AND the pastor or whoever does the ceremony.
As for requests during the DJing, if it is not the bride or groom asking I have a sheet of paper that they can write the request on and sometimes during the night I usually ask the bride to approve songs to play. I never play a request right away.
Also ask for games like Karaoke or other fun party games they want to do, those can require special music.
For the rest get the guide 🙂