To make recommendations, you can use different modal verbs such as Should and Could.

• Should is used to give advice or make recommendations :

– Affirmative form : Subject + should + infinitive verb (eg. We should visit the Eiffel Tour.)
– Negative form : Subject + should + not + infinitive verb (eg. We shouldn’t visit the Eiffel Tour).
– Question form : Shall + subject + infinitive verb (eg. Shall we visit the Eiffel Tour?).

• Could is used to make a suggestion of a possibility :

– Affirmative form : Subject + could + infinitive verb (eg. You could go to the beach)

We do not use couldn’t (negative form) to make suggestions. We only use couldn’t in a question to make suggestions :

– Negative question form : Couldn’t + subject + infinitive verb (eg. Couldn’t you go to the beach?).

Other sentences to make suggestions/recommendations :

– How about + subject + verb ? (eg. How about we eat at the restaurant?)
– Why don’t + subject + verb ? (eg. Why don’t you go shopping?)
– I highly recommend (+ subject + verb) or (+ object). (eg. I highly recommend you ride a bike or I highly recommend the Italian restaurant)
– I suggest + subject + verb. (eg. I suggest you buy a hat).