When asking for something in English, you would often use 'can,' 'could,' or 'would.' For example, when ordering food in a restaurant, an English speaker would say 'Could I have a steak?' or 'I would like to have a steak please.'
A mistake I often make (and I think many foreign students do so, too) is to literally translate these sentences into Chinese. For example 你可以给我一份牛肉面吗 (Could you bring me a plate of beef noodles?) or 请来一份牛肉面 (Please bring one plate of beef noodles). While grammatically correct, these sentences are too polite for the context of a Chinese restaurant. You can simply say like this:
I want a plate of beef noodles.
Bring me a plate of beef noodles.
Similary, when asking a friend for a small favour, say pouring you a soda, there's no need to be overly polite. Instead of saying 你可以给我一杯可乐吗? (Could you give me a glass of cola?) it is more appropriate to say：
Please give me a Coke.
The reasoning is that you are friends who have a close relationship, so there is no need to be too courteous. In fact, being too polite towards Chinese friends may make them think you don't really regard them as friends.
Lastly, there is often no need to thank people in Chinese. 'Thanks' and 谢谢 both mean the same thing, but there is a subtle difference in interpretation. Whereas the English 'thanks' is more lightweight, the Chinese 谢谢 carries a slightly stronger connotation, perhaps comparable to 'thanks a lot.' When you thank a waiter who has just served you your food, they will often say 不用谢 (You're welcome - No need to thank me). This is out of courtesy, of course, but saying thank you actually really isn't needed.