For me, even though I'm a right-hander, I try to use my left thumb to click on animals and crops since the gem traps are usually conveniently placed on the right hand side just waiting for you to fall for it. Keep in mind that for buildings, I use my right thumb since the gem trap is on the left, usually underneath the first thing you're cooking/crafting for you to quicken the timing. Since a lot of posters above have mentioned slowing down when you're clicking, using your weaker hand will automatically slow your reaction/clicking speed down, so you will exercise extreme caution and patience.
In any case, if you see pink (ie the pink gem trap button), stop immediately and run away!
I almost fell for the mining gem trap, when there's a popup asking you to continue mining, the gem trap is actually the bright green button on the right. It's actually preying on the lazy tendencies of players who can't be bothered to read, so avoid the obvious bright green button, and go for the low-key, gem-free, grey button on the left
Hope it helps