I think you should / ought to let your father do it.
(If I may make a suggestion -) why don't you ask Mrs Potterton?
I suggest we take the train.
Might I suggest we take the train?
My advice would be / I would advise you not to go.
My idea would be to invite them all at once. / If you ask me / ask my opinion / want my advice, I would invite them all at once.
If I were you, I would just take the money.
(If I were) given the chance, I wouldn't hesitate.
Be sure to take / Whatever you do, take warm clothes with you.
Under no circumstances let him have the money.
Make sure you have enough food in the house.
It might be / would be a good idea / wise / advisable / as well to tell your wife about it.
It is always a good idea / wise / advisable / as well to have spare fuses handy.
There is something / a lot to be said for doing the job oneself.
You should consider (the possibility of) having the baby at home.
What if / Suppose I were to lend you the money?
[infml] You might like / care to visit your uncle. / How about going to see your uncle while you are here?

[infml] - nieformalnie