It sounds like you may have a mild form of social anxiety, a common problem that affects close to seven percent of the population at any given time. Social anxiety is a fear of social situations that involve interactions with others, and is also associated with worries about being scrutinized or judged by others and coming up short.
While you suffer from one of the symptoms of social anxiety (your extreme nervousness upon meeting others), it sounds like you're still able to show up for social engagements despite your internal distress. This is a good sign, because one of the most effective treatments for social anxiety (and for many other anxieties as well) is to face that which you fear. You're facing your fears every time you meet someone new. This is very bold and courageous of you, and will serve you extremely well in your desire to transform your anxiety.
Eleanor Roosevelt once said "You gain strength, courage and confidence by every experience in which you really stop to look fear in the face. You are able to say to yourself, ‘I lived through this horror. I can take the next thing that comes along...' You must do the thing you think you cannot do.''
So, who cares if you're a little tongue-tied, if you say something foolish or if your palms sweat a little? I bet you won't be the only one in the room whose nerves betray you. And, it's better to care too much than not at all!
Don't get hung up in your missteps, rather, try to recover from them as quickly as possible. You might even try to make a joke, like, "Oops, I really stuck my foot in that one, didn't I? Here, let me take it out--(sound of foot being taken out of mouth)."
People tend to respond positively to someone who can laugh at herself; it shows she has enough confidence not to take herself too seriously. If you don't make an issue a big deal, others likely won't either. So try to suspend the harsh self-judgment.
When you're so focused on your missteps, you're no longer grounded in the present moment, where there are ample opportunities to forge a different impression. So, next time you call some guy you just met Cad when his name was really Chad, laugh it off and move on to the next topic of conversation, where perhaps you might have something insightful or witty to contribute, thus erasing your faux pas and forging a new persona, this one, not non-gratis.
The concern isn't to get over the anxiety, but to get through it, and the more you just keep showing up and laughing off those blunders, the more comfortable and confident you'll become.
Other Useful Resources:
Shaking Your Shyness, Renee Gilbert, Ph.D.
Overcome Social Anxiety, University of Texas at Dallas
Pay attention to how others interact when meeting strangers. Model their behavior if it seems reasonable for you, but be yourself. Don't model behavior that would not feel authentic.
If the problem is related to shyness, many people find that quality to be attractive so it could work for you.
We all like compliments. Initiating a conversation with a sincere compliment can start things off on the right foot.