How not to do a technical phone interview

Today I had a phone screen from a good startup from NY, even though at the time I felt I aced the interview on second thoughts I think I will not hear back from them. I actually took the call from skype and used a tool called call burner to record my performance.

After going through it I am not impressed at all, its not a tough interview but I managed to stumble or blunder couple of times.

Ok, listing my mistakes in order of worstness and why I made them.

1. Got the technical question completely wrong. The question is "How would you reverse a string without using a for loop". To be honest I was expecting a simpler question this question kind of got be off guard. So, I asked if I can use a while loop, he goes to say that I can't use a iterator. Then I got this idea of swapping start and end pointers until start <= end and he did not object to it. But on later thoughts I think he gave up on me, what he is actually looking for a recursion based solution. Its not simple or intuitive but a recursive solution can be made.
2. What is the difference between abstract class and interface, I have been asked this question probably 5 times in an interview now and I can't explain why I stumbled today. I was talking about implementing an abstract class etc.. while the main difference is in how many of them a class can use. A class can have multiple interfaces but can only have one parent class. Though I knew it I didn't say it.
3. I didn't get the company website before the interview, I actually didn't understand so I couldn't look at it.

I did some things ok and explained somethings good but overall it was an uninspiring performance. All in all I think it will be miracle if I am invited to onsite.

So what went wrong

1. I didn't take time when I have to a)while solving the problem b)while constructing sentences. I really don't understand my rush during the phone interview.
2. I am not getting the attitude of its ok to pause before attempting to say something. It creates a bad impression to mumble something than to pause a while and say something more coherent.

I hope I learn from this experience and would do better in future interviews.