Questions about "You're welcome"
 

"You're welcome" can be translated to どういたしまして, but I have never heard this said before in a conversation.

Do Japanese speakers just hardly ever use it?

I understand it is a formal way of saying "you're welcome", but even in everyday life we say "You're welcome", even though most of the time people respond with phrases like "no problem".

What are some informal ways of saying "You're welcome" in Japanese?

Also, where I currently work I am always responding with "You're welcome", and never with "sure", "no problem", etc...because it could be considered unprofessional here.
So my last question is: If I am in Japan and always respond with どういたしまして, will people look at me funny?
I've gotten so used to saying "You're welcome" after "Thank you" (even with my closest friends) that it may be difficult for me to break the habit.

We native speakers rarely say どういたしまして if ever. You WILL sound funny if you say it more than once a month. Let me shock you by saying that the first time I ever said どういたしまして out loud was in my 7th-grade English class, where we were taught to translate "You're welcome" into "どういたしまして". We hated it because it was in the active vocabulary of none of us. I guess you guys are doing the same thing where you live. (The first time I ever said あなた or わたし was also in grade 7. Yes, in my English class.)

We probably say いえいえ most often to mean "You're welcome." Don't get it mixed up with いいえいいえ as the latter is used for negation. Young people quite often say 大丈夫 or 大丈夫です to mean "You're welcome" these days, too.

You will also hear かまわないです（よ）、いいよ、こちらこそありがとう , etc.

Ah, thank you very much. I figured it would sound weird if I said it, but wanted to be sure.
Unfortunately when i was studying Japanese I learned that どういたしまして was "You're welcome", and I began to wonder if what I learned was correct because I never heard it after ありがとう!

Thank you for also providing me with some realistic examples of common responses to ありがとう!