There's physiological differences to be considered in becoming night proficient.
First, your vision has to be managed carefully. You can't just turn your gaze at something and see it. In fact, you WON'T see it that way, at all. One has to look "around" the object viewed, sort of peripherally view it, to see it. Scanning techniques become vital.
You have to learn how to conserve vision, too. Sufficient light to the purpose, and that grudgingly used, is my intent. A day pilot seems to buy the brightest flashlights available. Now, I have some pretty dim and small ones that I love. Dealing with over-illumination is an issue, too. It takes time to readjust, do you want to be picking your way out of the LZ while your eyes readjust? That's too much excitement for me, so if I can't avoid bright lights, and I know I'm going back into the dark- I close one eye.
You need to judge position with less external reference at night. That's not exactly correct- you need to learn to extract sufficient information from the larger picture, as you can't rely on detail being available. For instance, if there's a useful horizon, the inverse of how deep you are into the bowl of darkness outlined by the horizon is how high you are. Also, changing aspects of the shadows around you will be your clues to movement. It always strike me that my night touchdowns are harder but better- because I'm concentrating on fundamentals, I guess- stationary, slow descent.
If you're going to do serious nights, you have to spend considerable time shifting your body rhythms, or develop a strategy to deal with being sub-optimal, "jet-lagged," all the time. It reminds me of learning how to drink- how stupid will I allow myself to be before I hang up the keys? Hint- sooner is much better than later. If I'm reading the same WX report repeatedly trying to glean an understanding, the mental muscle isn't capable and we're not going.
Flight planning for nights is more critical than day flying. The world's asleep and unavailable, as far as facilities go.
Aircraft equipment becomes more important, too.
Night WX has a different dynamic than a day pilot is accustomed to. The WX goes down, down, down, over big areas, and won't get better until something changes it. At night you might not see WX until you're in it. Another hint- if you can't see through it, don't fly into it. It might be dark up ahead because something's obscuring the lights. The VFR helo pilots' natural inclination to reaquire reference to the surface by descending in reduced vis will kill you at night. I concur strongly that a professional has to be IFR trained, equipped and ready, to fly nights.
That said, vis frequently improves after sunset- less glare and light back scattered.
If you're new to it, take some time to fly with somebody who's experienced at night and can show you how to do it. Night flight has unique advantages and beauties. I prefer it, excepting the fact that it's so late!