Here's a few ways you can help yourself see better in lower light situations.

#1 Cover an eye.

Pirates wore an eye patch, so when they would maraud a ship they could fight on deck with one open eye, protecting the other eye with a patch.  Then when they went into the darkness below deck, they could uncover their other eye so they could see in darkness.   This could apply in several ways to you today.  If you get up in the middle of the night to say, use the bathroom, try keeping one eye closed while you are in the light, then when the lights are turned off, open the closed eye for much better night vision.  Your closed eye was already darkness adapted, you just protected it from losing that ability.

#2 Wear sunglasses often.

Wearing sunglasses in even moderately bright conditions will help your eyes maintain a better level of darkness adaptation and over time improve your eyes ability to see in lower light situations.   Sunglasses also protect your eyes, can prevent people from seeing exactly where you are looking, and can be used as a mirror to help you see behind you when sitting on a table.

#3 Allow time 

Give yourself time for your eyes to naturally adjust to darkness before you move if possible.

#4  Don't look directly into a light source

It kills resets your darkness adaptation time.  So don't look directly at any light source, including into a flame, at a monitor or at a light bulb.  This super intense light will saturate your vision with light, severely reducing your night vision.  Lower the brightness of your screens, condition your eyes to see better with lower light.

#5 Use your rod cells.

Your rod cells take about 30 to 45 minutes to adapt to a change of light around you. Rod cells can only see black and white and have poor resolution but are very sensitive in night vision circumstances.  Photopigments are chemicals contained in both rod and cone cells that are light-sensitive and convert what you see into a language that your brain can understand. Rhodopsin is a photopigment found in rod cells that is critical to night vision. 

#6 Don't smoke.

Smoking tremendously reduces your night vision.   Nicotine can cause your eye to stop producing something called rhodopsin, which is a pigment that is essential for night vision.

#7 Eat healthy.

Especially green leafy vegetables, fruits and stay hydrated.  Healthy fats, like fish fat. Bilberry is a plant that is used in making different types of medicine. 

#8 Look around the object

The cones of your eyes are better at distinguishing colors, the rods are better at seeing shapes and are better in low light situations.  So by looking slightly around the person, object or area you are trying to see in the dark, you will be engaging your rods, which should give you a slight night vision advantage.

Conclusion

Some advice said to wear red tented glasses before knowingly going into darkness, some implied this is a technique pilots have used if they could not sit in darkness to allow their eyes to adjust; I'm not certain it would matter.  I do know that using a dim red flashlight (filter or LED) does seem to help preserve night vision, and it's more stealthy at a distance, plus military maps are 'red light readable'.   Do take care of your eyes, make sure you are well rested and prepare your eyes with darkness or low light as possible before hand.   Delivering a strong blast of light on an adversary in an otherwise low light environment will temporarily, severely limit their ability to see in the darkness.   You can achieve this with a flashlight, or simply turning on a light in the room they are standing, then turning it off (to total darkness) before you enter, with already low light adapted eyes.