Use the Lowest Magnification You Can Get Away With
Bigger is always better, right? Not so with binoculars. The power (magnification) not only magnifies what you’re looking at, but also any shakes or tremors in your grip. The higher the magnification, the more your view will be shaky.
For those who have larger models, above the 10x range, you might want to consider getting a tripod or a monopod to support the binoculars.
Use Binocular With the Right Sized Objective Lens
The main lens at the front or your binoculars is called the objective lens. The bigger it is, the more light it will gather. In this case, more light = more detail.
Birding is best done at dawn and dusk, and so having a ratio of 5:1 between the objective lens diameter and the power is ideal. This results in a 5mm exit pupil which means a nice, bright detailed view. For example, a 6x30 gives you a 5mm exit pupil and a great view for that size of binocular. An 8x40 also gives you a 5mm exit pupil which is a great view for that size of binocular.
Adjust the Binoculars’ Center Hinge to set the Inter-pupillary Distance
The center hinge of your binoculars allows you to adjust the interpupillary distance between both halves of the binocular. When you get this right, you’ll get a nice round, headache free view of the world around you.
You’re not trying to get a 'figure eight' style view like you see in cartoons, just a single, round view that comfortably lines up both of your eyes.
Adjust the Eyecups for the Correct Eye-relief
The eyecups are there to position your eyes at the correct distance from the ocular lens (closest to your eyes). Most binoculars look best when your eye is 15-20mm behind the ocular lens. This allows you to see the image without any black shading around the edge of the image. The specific distance for your pair of binoculars is called eye-relief.
If you don’t wear glasses or use contacts, extend the eyecups out. If you’re wearing glasses, you should leave the eyecups close to the ocular lens.
Set the Diopter so That Both Eyes are Focused
Most people have some small difference in vision between their left and right eyes. To adjust for this, binoculars come with a diopeter adjustment. This allows you to adjust the focus of both eyes independently to make sure both sides are crisp and focused.
On most binoculars the diopter adjustment is on the right barrel. If this is the case for you, start by using the main focuser to get a nice sharp image in your left eye, and then adjust the diopter so until the right eye is also nice and sharp.
Bonus Tip - Use the Right Equipment to Clean your Binoculars
First things first: don’t use your shirt! Just like with your glasses, the fibers in your shirt will damage the delicate coatings on your binocular lenses. These scratches will cloud the view of your binoculars and reduce your ability to see fine detail.
As much as possible, try to keep fingerprints and water droplets off your binoculars. When you do need to clean them, make sure you get a soft brush or compressed air, as well lens pen or cleaning kit. When you use either of the latter two, use a gentle touch.