You're talking to a new client. You need him to sign a contract before you can work with him. You hand him the contract and say:
Skim over it and let me know if you have any questions.
You're a college professor. You're talking to a new class during the first week of school. You want to make sure that the students understand how important it is to do the reading assignments you give them. You say:
It's imperative that you keep up with the reading.
You're talking with a friend about a book that you read recently. You really liked it, and you think your friend should read it to. You say:
I highly recommend it.
To suggest that a person should do something, say "I recommend ___". For example:
I recommend the cheese fries. They're amazing!
I recommend hiring a lawyer early on in the process, to make sure that you don't miss anything important.
As you can see, you can either say "I recommend (noun)" or "I recommend (doing something)".
When you use this phrase, it just sounds like a simple suggestion. It doesn't sound especially bossy, polite, helpful, or rude.
It's common to include an adverb before "recommend". The most common ones are:
Doctors generally recommend keeping the sprain elevated, applying ice packs, and wrapping the area up tightly.
adverb, book, reading, recommendation 
You're talking to your friend about a book that you recently read. It was a really good book, so you stayed awake late at night reading it every night. You tell your friend:
I couldn't put it down.
book, interesting, reading, recommendation, simple past 
You're talking with your friend about a book you read. The book was very emotional and dramatic. You say:
Oh my goodness. It was so moving, by the end I was tearing up.
book, crying, emotions, past progressive, progressive aspect, reading 