let (someone) know

"Let me know" means "tell me". But "let me know" is a more polite and friendly expression. It's very common to hear in an English-speaking workplace:

If anything comes up between now and then, just let me know.

You can also use it with friends:

Let me know when you're finished with the computer.

please, please, please

You can emphasize a request by repeating the word "please". For example:

If you have any money problems, please, please, please come to me.

Please, please, please check with me before signing any legal documents.

This is typically only done in spoken English.

anything I can do to help

If someone is having a problem, but you're not sure how to help, you can ask:

Is there anything I can do to help?

This shows your support for this person. Another way to phrase this which is more formal but more distant is:

If there's anything I can do to help, please let me know.

This phrase is good to use when a friend or acquaintance has bad news about an illness, a death in the family, money problems, etc. You can also ask "Is there anything I can do to help?" when you see someone working really hard and you don't have any work of your own to do.

help (someone) through (an emotionally difficult time)

"Helping someone through" an emotionally difficult situation like:

• a divorce
• a death in the family
• drug addiction
• being laid off from a job
• depression

...means listening to them, helping them, and being nice to them until the bad situation is over.

You end this expression with a phrase that describes the time period or names the situation:

He helped me through a really difficult time in my life.

She really helped me through the divorce.