Parkng book in advance to get the best possible rate.
Check whether you can pay for fast track on the day through security/passport. Sometimes the normal queues are so short there is no point paying, equally if the queues are huge cough up the cash on the day.
Have never come across a good value ‘premium lounge’, see if your credit card or other membership gets you into an airline specific one. Otherwise try and limit the time at the airport, as it is normally the time post check-in where you get fleeced for food, drinks and triangular chocolate!