Don't use "let's" if you are giving someone a suggestion.

I read stuff like this about an event:

• × Let's check it.

I know the author is trying to sound casual and cool while suggesting that I attend. It's just that the English is all wrong. What the author wants to say is:

• ○ Check it out!

"Let's" means "let us". That means the person you are talking to AND you. If you don't intend to do it together at the same time, don't use "let's".

Usually the true meaning is an imperative sentences. Most Japanese avoid imperative sentences in English because they rarely use them in Japanese. They never say 「それを見!」 They might say 「 御覧ください」or 「それを見って」with friends (any advice from you kind readers about the Japanese I've just written would be appreciated. Email me!).

In English, though, there's lots of ways that are direct but not impolite. You will hear people say:

• "Take a look!" or, more politely, "Please take a look."
  
• Look at that!

Depending on the tone of the speaker, they may be perfectly OK.

Compare these two:

• I know a nice restaurant in Ginza. Let's go when you have time. <- I want to eat with you.
• I know a nice restaurant in Ginza. Here's their card. Go check it out if you have time. <- We won't go together.

Don't hesitate to ask me if you have a question. <- imperative

Let's talk about this again if it's not clear to you. <- We'll discuss it together.