How can I keep stink bugs out of my house?

I hate to use the word “infestation,” perhaps more for my sake than anyone else’s, although I only see them periodically, but I’ve got a Brown Marmorated Stink Bug infestation. Do I really need to hire an exterminator? Can I do something to deter them from hanging out in my house? I already have screens on all my windows and my seals are tight, since this house is only 5 yrs old.