Translation of "Faire signe à quelqu´un" in English ?

How do you say in English, "fais moi signe" :

- "Let me know when you are available" in the sense of telling me when we can have a talk by on Italki for instance - "Let me know when you are available" is correct but it can seem a bit formal. Informally you can say "Let me know when you're free" or "Tell me when you're free"

- Or "Get in touch" in the sense of giving getting/receiving news from you. - "Get in touch with me..." or "Let me know..." or "Tell me..."

- In what context do you use : "make a sign to me" - "Make a sign to me" is the literal translation of "fais moi signe" and wouldn't be said in English. It is translated as "Give me a sign."

You would say "give me a sign" to someone in advance of a time when you know that you will not be able to speak to each other about something but, you still need to communicate about it. Gestures are usually used to give the sign. Example;

- "Give me a sign when you see him coming back."

- "Ok. I'll shake my head."

I hope this helps you.