I have difficulty recognizing faces. It's not something I realized I had difficulty with when I was a child, but looking back on my experiences, it seems that I've had this difficulty all of my life.
When I was a child, I thought I just had trouble remembering names. This is something that many people say that they have trouble with. I had never heard of prosopagnosia, so the closest description I could find to what I was experiencing was a problem with remembering names.
But, for me, it was not the names, but the faces.
Since I have trouble recognizing faces, I rely on other clues, like hair color/style and voice.
If people appear similar in other aspects, then it is hard for me to tell them apart.
One of my earliest memories regarding this problem is that in school sometimes teachers would have students pass back graded papers. I dreaded doing this task, because I had trouble telling some of the students apart.
I tried working in a bagel shop, but that only lasted a couple of days. I was so busy trying to fulfill the orders, that I forgot to look at the people to remember who ordered what. This caused some frustrated customers (as well as a frustrated me!) I'm sure I appeared dumb, but really I was just coping with a difficulty that I wasn't aware I had.
About 4 years ago, I came across information on prosopagnosia (thanks to the marvelous internet) and realized that described my condition accurately! Since then I have been actively practicing to increase my ability to recognize people and faces.... I am getting better, although I'm not sure whether my ability to recognize faces is actually improving, or whether I'm just getting better at picking up other clues to remember people!
I watch TV shows and movies and try to recognize actors. This used to be an impossible task, but now I am able to do it some of the time. I think I rely on the sound of their voice as much or more than their face. It's just easier for me.
I still sometimes get lost when watching a movie that has multiple people who look similar, and this can make the plot impossible to follow... A very frustrating thing!
I have been taking piracetam to try to improve some of my cognitive skills. It's an interesting drug (sold as a supplement in the USA). It works on the brain by somehow increasing or improving neural pathways, or at least that's what it seems to be doing. It's not a stimulant, but rather a nootropic (a smart drug). Since it changes neural pathways, it can have some effects on mood (both positive and negative), but that's not the purpose I take it for.
It seems to help me with recognizing people, language skills, and word retrieval. I had speech and hearing problems as a kid and so I still have some difficulty in that area, and it seems to me that piracetam helps. If I take it before watching Jeopardy, I can usually get more answers right because it seems that I can think of the answers faster. That all too common "it's on the tip of my tongue" experience goes away.
For more details on face recognition disorder, check out Cecilia's description.