I Think it is her time...

So I have a leopard gecko that seems to be completely miserable and i think it is her time to go... What is the best way to euthanize her? I heard people freeze them and some other crazy man said he cuts their heads off with scissors. What is the best way to put her down? Thanks.

Neither of those options are really acceptable or humane. Freezing is very painful for the animal. Cutting their heads off with scissors sounds like it could go wrong and then you'd have a suffering, bleeding animal while you struggle to finish the job.

So what do you think I should do?

From what I've heard, total brain destruction or severing the head completely work and are more humane (just don't use scissors)

With snakes pithing the brain is preferred - meaning, total instant destruction. Heavy mallet or hammer to the head, knife to the brain, etc. A .22 directly to the brain would also work, but not an option if you can't legally discharge a firearm in your back yard.

Freezing is not at all humane, please don't do it.

You could also take it to a vet to be put down. Was one treating her already?

Yup, destroy the brain, unfortunately.  Sounds rough but compared to other options, it's the least painful to the snake. I'm not sure if a vet can euthanize a reptile but it would be worth calling.