Can anyone tell me what is involved in going through customs when arriving in bonaire and aruba?

Not much is involved.
The Bonaire entry about the fastest and easiest customs entry I have seen anywhere. The agents are polite and move you right along.

I have been through outgoing US pre-customs screening on Aruba a couple of times. Still don't know what that's all about. Still had to go throught customs in Miami.
Clay

Unfortunately, with the growing "fame" of Aruba as a drug transfer point, the pre-customs screening there seems to be about drug interdiction. Sad.

And what method is employed in the 'pre-customs screening'in Aruba? Is that coming from the US or going to the US?

I believe the "pre-screening" in Aruba is for Immigration, not for Customs. That is why you normally sail right through Immigration upon arrival in Miami or Puero Rico, but still must clear Customs.

>>And what method is employed in the 'pre-customs screening'in Aruba? Is that coming from the US or going to the US? <<

That's going to the US. As I recall, it involved filling out a form. See Susan's reply.

I think you are right Susan. I do seem to remember "immigration" being on the sign and a form to fill out which would have been the immigration form.