You will be given paperwork to complete, on the plane. It's just name/address/passport #, etc.
If from the US, this is all we have had to do.
If taking anything into Bze., from US, that is not what one would generally use for vacation use, there is a customs claim form that you will also need to complete. It's also given to you on the plane, while in flight. If taking nothing, you still need to indicate that with a '0' ( zero ) dollar ammount.
Example: Christmas gifts in the packaging. Parts for vehicles etc. They MAY search your bags.
Honesty pays or you do if they do a search. It's random.
If you have been there many times, they may automatically search since you MAY have established friends and friends ask for gifts or items not generally used for vacations. Many people/items get past customs, some don't.
Declare them or, again, you may be searched.
You may not be a target at all, just routine.
If you do declare, you will need to pay customs on the extra, non vacation items.
It's all easy, it just sounds difficult.
Enjoy your stay.