The important thing is to catch him (or her) in the act.
Reprimand only as they are peeing/pooing, not after! He needs to know that the action of peeing/pooing (in the wrong place) is bad, and not that the pee/poo itself is bad! I used to scold Teddi every time I saw pee/poo in the house. This didn't teach him anything except that if Mommi saw the pee/poo, then I'm in BIG trouble! He didn't seem to understand that the act of peeing/pooing will result in pee/poo
Of course, the only way to catch him in the act is to watch him all the time. If you can't, then put him in a crate or keep him in an enclosed area until you do have the time.
Also, reprimand doesn't mean spanking, shoving his face in the pee/poo, or anything physical. All you need is to say/shout "Bad boy!" in a really evil-sounding, deep, you're-in-trouble voice. (Works for me!
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The second part is to teach him where you would like for him to pee/poo, whether it'd be on a pee pad in the house or outside on the lawn. I do this by saying "Good boy!" in a high-pitched, I'm-so-unbelievably-happy voice as he is peeing/pooing where I want him to (in Teddi's case, outside on the lawn). I still do this even now so he'll never forget that I like him peeing/pooing outside! In fact, he only poos (for the most part) when I take him out because no one else is as happy as I am to see him poo!
My training regime with Teddi (when he was less than 6 months old) consisted of watching him like a hawk and/or keeping him in an enclosed area. Then I took him out every 1-2 hours. When he peed/pood outside (where I wanted him to), I praised him, and when he peed/pood inside (where I didn't want him to), I reprimanded him. He eventually got the hang of it within a few months!
I definitely remember the frustration when Teddi was still housetraining... Like everyone says, just be patient and stick with the plan!