I was doing quest and got 4 of these amulet things which I think are worth more than you can sell in your shop. So I'm assuming I'll put in trade then? How do I know how much to price them?

You can sell things in your shop for up to 100,000,000 now. If you're talking about and the rest of those, you can certainly sell them in your shop. They're usually worth 300k-400k, just paste their names in the shop search to see what they're worth.

edit: or hover on the item in your inventory and click the shop search button

while putting stuff in your shop is easiest and most likely to get you a quicker sale, there's no reason you couldn't Trade them if you wanted to. Go Commerce - Trades - New Trades and set yours up. You can have up to ten items per trade, and can offer/ask for scrip, CSC, items, or any combination of those.

There is a Shop Search feature that will tell you what most items are worth, and Subetalodge's Item Database isn't too far off. If you can't find a price in either of these places, there's a subforum that's all about users helping you (in their own rather opinion) pricing. Do a Find on "pricing" when you're on the Forum page.

In the end what something's worth is what it'll sell for, compared to how soon you need the scrip. If you need it sooner, drop the price. Keep in mind the average user has only 13MsP.

The only amulets I've seen from Quests are shop-sellable IMO.