Please, help me with conditionals!!!

I was am [using past tense means that you are no longer having a problem with them] faced with the following problem in English - conditionals.

Please, can tell me what the differences between among these words, "could", "would" and "might" in second and third conditionals?
Also I really cannot understand mixed conditionals...

First of all let's talk about the present tense form before going into the past form.

can    the ability to do it.    

will    have the determination to do it.

may   iffy, undetermined at this point if something is to be done.  Sometimes, imply you have the                permission.

shall   This one is tricky.  It is a bit more determined than "may".  However, in law it becomes "will".

          "I shall do my homework" is weaker than "I will do my homework".

          "Thou shalt not kill"  - a command.

          "he shall die"  - depending on the situation and depends who is saying it.  If it's a doctor for                  example, the doctor is quite certain the patient will die but there are chances that he may pull 

           through.  If it is the King who said it, then death is inevitable.

ought  You have an obligation to do it.

must   No other choice but to do it.

The past tense of "can", "will", "shall" and "may" are "could", "would", "should" and "might".  Some consider the past tense form is more polite in a question.  "Could you hand me the butter?" sounds more polite than the present tense form which is seen as very assertive. "could here means that, if you have the time, if it is not inconvenient, then pass me the butter".  Again, it depends on the situation.  In a business setting, the present tense form is favoured because you are seen as an assertive person who is in charge etc.  Here's an example, "You can kiss me but you may not!"  What it is saying is, "You have the ability to kiss me but you don't have my permission to do it!".

"should" is always seen as the equivalent of "ought". e.g. "should I do this?"  Or that it can mean that you are pondering if you want to do it.  All depends on the tone you are saying.

"would" is seen as perhaps/wondering.  "Would he kiss me?"

Hopefully, the following links for 2nd and 3rd conditionals will help you. [I never know what they are until today! We never studied so in detail unless you want to be a linguist!]

http://www.englishgrammarsecrets.com/firstconditional/menu.php

http://www.englishgrammarsecrets.com/secondconditional/menu.php

http://www.englishgrammarsecrets.com/thirdconditional/menu.php

http://grammar.ccc.commnet.edu/grammar/conditional2.htm