Bengi had his ears down when I got him. I did some research so I trimmed the hair in the ears and taped them following the steps in this webpage:
http://members.cox.net/jrogan/ears.html
I left them taped for 3 days and it worked! When I would see that one of them started to go down I would taped it for 1 day. They were both up for about 2 months.
Then, at about 4 months old, one ear when down because he is teething. I waited like 2 weeks but didn't come up. People say it's normal, but I was impacient, so I trimmed the hair and tape it for 24 hours. It worked! It's been like a week now, and both are still up.
I found out it is really important to keep the hair trimmed for the first year. Specially for the puppies that had them down for their first 3 months of age, or they went down when teething.