This tip, concerning your front door, is a bit of a combination of some of the other tips that you've probably read here before. 

The front door should make a good impression as people come to look at your house.  Besides the overall appearance of your home, the front door will be one of the first things the potential buyer will see!

First make sure that the lock works properly and easily so that when the agent comes to show the home, the buyers don't have to stand around while the agent takes out his lockpicks

Make sure, obviously, that's it's clean, nicely painted and the knob/fixtuers are polished.  If you have a nameplate/plaque that has your family name on it, change it to something neutral, again, "de-personalizing" your home.