You COULD go to medical school and become a Neurosurgeon; but just because you COULD to that, it does not logically follow that you would want to do that.

I hope this helps. Write again if you would have me offer more suggestions.

I COULD give more examples and I WOULD be very willing to help you if I COULD.

I WOULD help you if I COULD help you but you see I cannot help, because I COULD not think of enough answers to your question. If I COULD think of answers to your question, then indeed,

I WOULD help you. I WILL help you when I CAN help you; but perhaps in this instance I COULD not help you. I WOULD always try to help others if I COULD help others; but I cannot always help others even when I am "willing" to help others.

When you think of COULD, think of it in terms of a specific SKILL or POTENTIAL you have to do something.

If you were a lawyer, you COULD represent someone in a court of law; but that does not mean that you would want to represent an evil criminal in a court of law.

If you were a Queen, you COULD order the execution of any citizen of your country without a trial; but that does not mean that you would want to order the execution of any citizen of your country.

If you found a man that you liked for a friend, you COULD date that man; but that does not mean that you would want to date every man that you liked for a friend.

If you were wealthy, you COULD enter into the manufacture of a line of custom made exotic sports cars that cost $500,000 each; but that does not mean that you would want to do that simply because you COULD do that.

I think the difference is going to still be "fuzzy" for you. So let me show you a better way to choose between the word you employ when you write.

When you think of WOULD, I want you to think of its association with WILL.

I also think you should associated WOULD with WANT, which is another derivation of WILL.

When I WANT something, I am WILLING something. You can think of it this way.

Those things I WANT in life, I apply WILL to in life. I WOULD have those things come true.

"I will write an answer to Kate, because I know an answer."

"I would write an answer to Kate, if I knew an answer."

"I will help because I can help." or "I would help only if I had the time to help."

"I WOULD have the world to be a peaceful place, because I WANT the world to be a peaceful place."

  I will try to help you to understand with some examples Kate.

   Imagine this is you writing.

   "I would get an answer to my question if only someone would help."

  "I would speak English, if I could pronounce the words."

  "I could speak English if I was willing  to study."

   "I could master the language if I studied with great effort."

   The meaning and usage is difficult for you because the words are not entirely different.

I can write for example, sentences like this:

  "I could answer your question if I knew the answer."

  "I would answer your question if I knew the answer."

 The dictionaries inform us that    COULD shows "possibility" or what can our could  possibly be done.

  WOULD   is stated to express "desire" or "intent".

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Thank you very much !!! Bruce.  I will follow your rules to use these two words.