should vs. could

[Nathan Smith]

Could someone give me examples of each and the rules that apply, please.

1000 thanks
Nathan

[Milanya]

Should
"Should" is most commonly used to make recommendations or give advice. It can also be used to express obligation as well as expectation.

Examples:

When you go to Berlin, you should visit the palaces in Potsdam. recommendation
You should focus more on your family and less on work. advice
I really should be in the office by 7:00 AM. obligation
By now, they should already be in Dubai. expectation
http://www.englishpage.com/modals/should.html

Could
"Could" is used to express possibility or past ability as well as to make suggestions and requests. "Could" is also commonly used in conditional sentences as the conditional form of "can."

Examples:

Extreme rain could cause the river to flood the city. possibility
Nancy could ski like a pro by the age of 11. past ability
You could see a movie or go out to dinner. suggestion
Could I use your computer to email my boss? request
We could go on the trip if I didn't have to work this weekend. conditional
http://www.englishpage.com/modals/could.html
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con·text - The part of a text or statement that surrounds a particular word or passage and determines its meaning.

[Bulone]

I think Alex's esl lessons from youtube would help you understand this usage.