I have asked many people about "best to way to clean cauliflower" before cooking. I got several answers, like keeping in salt water or add soak in turmeric mixed water. And also how do you remove worms from cauliflower?
A bucket of salty water is the best way to get rid of bugs. That said, I've never had a problem with bugs in store-bought cauliflower.
You need to completely submerge the head in water, so a bucket that can fit the whole head is best. Add about 2 Tbsp salt per quart warm water to get it nice and salty. Submerge the head, florets down (they float, so a weight to keep it submerged will help). Let sit 5-10 minutes, remove, rinse, and eat as you please.
The salt in the water helps to kill the bugs and encourage them to let go. It also might kill some surface contamination if it exists, but this isn't really the point. You should see bugs either floating or at the bottom when you remove the cauliflower.
If you don't need the head whole when cooking, core and cut into desired size prior to soaking.
I actually break it apart into the size you want to cook it and then let it soak in salt water (this help get into the crevices). Then, toss into a collinder and spray with a sick sprayer while shaking. I do this with similar veggies as well.