Oh my goodness just the post I need! Yes closing on time is a major issue that I have run into. It has almost made a couple of my buyers lose their house because the lender they chose had too many delays!
I agree with Ivy that transparency to the buyer and to their agent is key. Many first time homebuyers have no idea how the process works and don't know what questions to ask to make sure they are doing the right things to be able to close on the house they want. Also being straight forward and honest about timelines. Many lenders seem to try to give overly optimistic idea of when something will be completed and that stresses the listing agents out because when that date comes and goes, they don't know what is going on.
Answer the phone and texts as soon as you can, within the same day if possible. We have to do that as well for our clients to keep them updated :)
I look for lenders with low fees for my buyers. One of the ones we are working with right now, offers $100 per diem to the seller if they close later than they promised. We are about to enter escrow with him so we will see if that happens or if he does close on time. That means a lot to the listing agent and Seller as they see your lender is extremely motivated to honor the contract and keep on top of the loan.
Best of luck!