Here are some ways which we can give give advice or make recommendations:
For example, imagine that your friend is worried that she is getting fat. She asks you for some advice. You can respond using the following phrases:
You should take some exercise.
You ought to eat more fruit and vegetables.
Why don't you go jogging?
How about eating less sugary food?
For stronger advice you can use 'have to' or 'must':
You must see a doctor
You have to take her to see that movie. She'll love it!
There are two ways which we can use 'recommend' and 'suggest':
I suggest taking a holiday.
I suggest (that) you take a holiday.
I recommend going to bed earlier.
I recommend (that) you go to bed earlier.
We can use imperative verbs + '-ing' to give advice. Let's look at some more examples using your fat friend!:
Start going to the gym.
Stop drinking so much coke.
Consider switching to brown bread and rice.
Try cycling to work.