1) Preparation-If you leave things behind such as binoculars, field guide, camera, scope, batteries,field notebook,directions, jacket, or any other needed items it can put a real damper on things. Not leaving early enough can also detract from the day.
2) Sleep-Feeling well rested definitely enhances the day. I tend to be more perceptive in my hearing and vision. I am also much more enthusiastic if I've had a good night's sleep.
3) Weather-You can adapt your day to do some form of birding in any weather conditions but a pleasant day can enhance the overall experience.
4) Location-Exploring a scenic area, hot spot, or a location that you've never tried before can make things more interesting.
5) Birds-Seeing lots of birds, a good variety of species, interesting bird behavior, or new species can definitely help make it a great day of birding. Discovering a really rare bird can make for an exceptional day.
6) Optics-Having superb optics makes everything look so much better. It's not just the quality of the optics though. The viewing conditions- (lighting,air quality etc.) have a definite effect on the performance of whatever optics you do have.
7) Season-There are certain days in each season that exemplify the beauty of that particular season. -The perfect Spring, Summer, Fall, or Winter day.
8) Time-I probably should have put this one higher on the list. Not having any time constraints allows you to bird at a much more relaxing pace without feeling that you have to squeeze everything in.
9) Food-It's nice to start the day with a cup of coffee and breakfast of your choice or perhaps hold off on breakfast till a little later in the morning.
10) Company-Although I enjoy birding alone, it's nice to go birding with others for a change of pace.
Which of these would make it to the top of your list? Do you have any that you'd like to add?