Make sure you understand when and where the moon will rise and set as well as where it is within its cycle. Full moons make it much more challenging to see stars, planets, and constellations. It is best to go during the new moon.
Once the sun has set, you want to be sure that you keep your night vision eyes adjusted to the darkness. Avoid lighting and car headlights if at all possible. Consider getting a red light filter for any light source you use. This will help you keep your eyes adjusted to the night’s dim light.
As they say, the early bird catches the worm. There is a definite difference between trying to birdwatch at sunrise versus trying to birdwatch in the afternoon. The quantity, quality, and frequency is staggeringly lower later. Birds prefer early morning and cooler temperatures. Normally they start to drop off in activity and calls mid-morning.
Get a bird guide for the type of habitat that you will be in. For example, birds of Southern California or wetland birds. There are field guides that fold up and are laminated, while there are other books that are heavier in size and material and won’t be as easy to carry without a backpack.
Get yourself a good pair of binoculars and maybe even a harness so that you can be hands-free. You want make sure it has some of the following features: good magnification (likely 8 or 10), good field of view (likely 32 or 42), water/fog proof, and rubber coating.