It's like everything else, practice is pretty critical. I've read sources that say it's somehow disrespectful to use tarot readings for frivolous or casual questions, but my experience is that the need to practice and learn your own way of reading and interpreting, as well as understanding how you connect with different decks, trumps. If you're new to reading, I'd strongly suggest doing a daily reading with a light question or none at all, just to get used to understanding how what you read reflects in your life. If you're practiced and do readings regularly, I'd suggest you use different decks, because sometimes different decks resonate with different moods and situations.
There are times when I simply can't read right, and it's good to learn when those are for you, too. Emotional upset, physical illness; not all states affect everyone the same way, so I found it really helpful to know when I simply can't get a good interpretation no matter what, and what states I can be in and get sharp, very successful readings. It's not always what I expected; for instance, I can get very clear readings when I'm physically ill.
I love those readings when the answer is so blazingly clear, you remember them for years, and they stay relevant.