Start by asking....if you do not ask, you do not get. Ditto on hotels. I never use the intermediary booking services - in phoning the hotel direct, I get just as good deals and often can nail the upgrade. On points cards, never pay for a suite use the points. The Hyatt per night is 20k per room, whereas if you take the cheapest room going and upgrade, you can get a suite for 2000 to 5000 points for 4 nights........
If it is your first flight with them, unlikely it will happen.
Let them know if you have a special event like a birthday or anniversary - you can't just pull this one all the time.
Get to know station airport managers.......always useful
(One advantage of having a Platinum Amex is that they do offer free use of a lounge and there are often upgrades on hotels going)
Send in complimentary letters as well as complaints, it shows that you are balanced in your judgement - some airlines 'save' them and record.