In the freezer. use amber glass bottles, get something with a good liner, polycone or PTFE or something like that.

Use small bottles. You don't want to be using one big bottle and having to take it out refill your supply all the time. It's easier to just take out one small bottle at a time to work with. My nic is 100mg and i use 30ml bottles.

Nic is dangerous obviously, so you need to make sure no one can get to it and poison themselves. If you can't put it your freezer safely, still get the nice bottles. They are air tight and will keep the light out at least.

Mine sits on my desk. Turns a little yellow after a year but it still nicotines.

I keep my VG-based nicotine in 30ml amber glass bottles, in the freezer in a cardboard box (to keep from exposing the bottles to light every time the freezer door is opened).

Here is the article that made me decide to keep my nicotine stored this particular way (I'm not affiliated in any way): nic storage

I just opened a fresh bottle of nic juice that had been sitting in my freezer, unopened, in its original brown glass bottle. Fresh as the first jar I opened last year!! This stuff will freeze for a VERY long time if done properly.

Clearly marked in the freezer is what you want. The fridge has the possibility for moisture and mold to build up and you don't want to vape that.

The info sheet that came with my Wizard Labs Nic/PG solution states 34-41°F is optimal storage temp and for long-term storage keep it in glass in a dark area for up to 18 months.