Hi Leslie "Hazme saber" and "dejame saber" is the same, but, "dejame saber" is not common and not sound natural, if you want to sound better you should use "Hazme saber". Example: "Hazme saber si necesitas ayuda con la tarea" When you say "Hágame" you are doing in formal way. for examen if you would be speaking with old people, a teacher, your boos or someone that you respect obviously, you have to use "Hágame". Example: speaking with you grandfather - "Hágame el favor de avisarme si necesita ayuda" Really I hope I helped you, I am learning English if you see mistakes you will know why.

Hey Leslie! I have a lot of friends who are second-generation hispanics in the United States, and from them they have told me that "avi'same" works just as well as "de'jame saber", stemming from the verb "avisar", meaning to advise when used in this context.

Hola Leslie, I think this is a great question. It seems to me that "Hágame saber" is different in two ways: - First, it can denote an imperative form of speech - a demand. - Second, it could also denote respect. In everyday Spanish, at least in latin america, I would say "Déjame saber" is more popular and commonly used, followed then by "Hazme saber." If we look at literal meanings, hazme is closer to "Make me know", whereas déjame is closer to "Let me know". I think therefore that "Déjame" is a gentler proposition. Lastly, you can also turn the gentler "Déjame" into a respectful "Déjeme". Hope this helps!