I don’t know what to + (verb)

You are letting someone know that you are not sure about what is being asked. You may also have no knowledge or opinion on a topic.

Here are some examples:

“I don’t know what to eat for dinner.”
“I don’t know what to buy you for your birthday.”
“I don’t know what to say.”
“I don’t know what to do with my spare time.”
“I don’t know what to do for vacation.”
“I do not know what to do to make you happy.”
“I do not know what to do to help you understand.”
“I do not know what to think.”
“I do not know what to do to prevent this.”
“I do not know what to order.”

I should have + (past participle)

‘Should’ is the past tense of the word ‘shall.’ When using the words ‘should have’ you are talking about something in the past that you ‘ought to’ or ‘might have’ done.

Here are some examples:

“I should have gone with you.”
“I should have studied more for my test.”
“I should have read the directions before starting.”
“I should have eaten breakfast this morning.”
“I should have listened to your advice.”
“I should have married her when I had the chance.”

‘Shall’ is something that will take place or exist in the future.

Here are some examples:

“I shall leave tomorrow.”
“I shall finish the job next week.”
“I shall see it tomorrow.”
“I shall go outside if it’s nice out.”
“I shall pay for this later.”

I wish I could + (verb)

You are expressing a desire to do something.

Here are some examples:

“I wish I could sing better.”
“I wish I could settle the argument.”
“I wish I could sail around the world.”
“I wish I could remain calm during all of this.”
“I wish I could remember his name.”
“I wish I could replace my old car with a new one.”
“I wish I could play outside.”
“I wish I could go to the game with you.”
“I wish I could write better.”
“I wish I could own my own business.”