How should I drive when i'm karting? How should I do in the curves? Tell me, please! I really want to learn 
Mate when I do it, I go by instinct. Just remember the less you turn the wheel in a kart, the faster you go in the laptimes.
Rule of thumb in tight curves is as what zurich_allan said earlier....you keep the kart as straight as possible while making the corner. Most importantly, you focus on your reaction time to oversteer (rear end of kart slipping away from you) and how quickly you can correct it. If you find yourself spinning a lot in your first tries, you either need a lot of practice or just don't possess the reaction time or feel of a kart.
Just re read zurich_allan's post, it's not long but has a lot of good feedback. Karting is not about reading a textbook on how to go about it, you just need to get behind the wheel and learn your way doing it!

Btw, do go for at least a 100cc or above...you're wasting your time with the ones less powerful, they're more 'fun kart' version for families to enjoy. You might want to start off with a 100cc and then try the 120cc...if the track offers 150cc grab it! That has some serious power which doesn't really depend on your weight. I weigh around 75kg and when I first started karting (around 70kg), I was told I'd be at least 5 - 8 seconds off the laptimes no matter how good I am if I used karts below 100cc. Guys who weigh around 60-65 have a major advantage with the crappy karts.