"You should do X" is a suggestion. If someone asks you "What should I do today?" You could respond, "You should read a book." If you tell someone they should do something then you are indicating that, whatever they should do, is the best option. "You better do X" is more forceful. It can sound threatening. The assumption is, if you do not do X, then something bad will happen as a result. "You better go to class" implies that not going to class would be bad. "You could do X" would be used if someone has multiple options or if the outcome of something it's overly consequential. When in doubt use "You could" because it doesn't show you have an opinion.

Could is used when it is an option you can take, or a suggestion; should is when it is something the speaker thinks would be better than other options, or that it is the correct course of action. Better acts just like should, but is much more informal. so, you can use "you better" with friends, but with a teacher or in writing it is better to use "you should".

1. "You should take a rest" This is how you give someone advice. It means it that you think it is advisable for that person to take a rest. A doctor would say this to a patient, a parent would say this to a son or daughter (and vice versa), or a friend would say this to another friend. You wouldn't normally say this to your teacher or boss unless you had quite an informal relationship with them. 2. "You better take a rest" Don't say this - it is bad English. Just look at it - there isn't even a verb in the sentence, is there? The correct version of this is "You'd better take a rest". The 'd' is a contraction of 'had'. For this to be correct English, you need to include the 'd'. "You'd better take a rest" is a stronger statement that 'should'. The implication of 'You'd better..' is that there may be bad consequences if you don't take a rest. For example, we often say "I'd better go now", meaning that if I don't go, I'll miss my bus or be late for work. 3. "You could take a rest." This is just a suggestion. Whereas 'should' is your opinion, 'could' is not your opinion: it is simply a statement. You're saying that it's possible for the person to take a rest if they want to.

Thank you very much.

You better take a rest or You had better take a rest more of a serious warning than a suggestion.