Credit score

I was scared to get my first credit card too but I knew I had to start somewhere. Last year I got one from the same bank as my debit card and only use it for small or 'fun' purchases ie gas, going out for dinner, etc. I have it auto-debited to pay whatever I spent every first of the month. (The minimum payment each month is $15, but I like to pay in full so I don't fall behind). 
The analogy I heard was a credit card is like a safe, so if you have a credit limit of $1000, the banks like to see that you'll borrow 20-30% ($200-300) and put it back. Sometimes I've spent more than that but that's why I like to pay in full each month. Its a good habit to keep because if you don't pay in full, the credit card company will add interest to whatever you didn't pay back so you'll end up paying more money to "borrow" it.  

Maybe others have alternative ideas of how they see it? 
I hope this helps! (#plug...I have the app Mint as well which categorizes payments and shows you what you spend the majority of your money on. I spend it on Food & Dining...whoops  )