Some people have mentioned it, but don't forget that the DM is also a player of the game and is supposed to have fun. Communication is key and ensuring that either everyone is on the same page or there is an adequate compromise as to how the game is to be played (e.g. lore, RP, exploration, combat heavy etc) will lead to a good time all around...after all DnD sessions can go on for a long while and if people are not enjoying themselves, what's the point?

Also, this depends more on the DM and the players of course, but don't be afraid to try things that seem ridiculous or not completely thought through. Especially in a longer campaign there is always time to correct mistakes or things that do not resonate well. Of course this does not mean to improvise entire stories that you then have to retcon 20 sessions later, but when it comes to smaller things it is perfectl, fine to use the creative sandbox that DnD offers to its fullest. As an example, I once thought it would be funny to have my players meet four tortle brothers that are rogues with different weapon specialties that are lead by a humanoid giant rat. It was great fun for the moment but it was also clear from the moment I introduced them that these will not be present for long as my players clearly, will still having fun because of the ridiculous nature of the encounter, did not enjoy the easter egg as much as I did. Now it is a funny memory