Har du några Star Alliance points att använda för din uppgradering finner du info här. Om inte så hittar du ett telefonnummer i länken nedan där du kanske kan få hjälp.
Turkish Airlines - Upgrade - turkishairlines.com
Turkish själva skriver på sin hemsida att priset för uppgradering är cirka 30% från högsta ek biljett räknat. Nedan en liten artikel om hur det är om man försöker få sig uppgradering vid gate/i planet.
Operational Upgrades
One of the common questions is "How do I get an upgrade on Turkish Airlines to Business or Club class?". Alas, Turkish Airlines has the friends and family upgrade scheme you've often heard about, but rarely seen in action. What this means is that if you are family of the pilot, the crew, or the man who loads the bags - or even just a casual friend having met them in a bar years ago - you'll get to sit in the comfy seats. Everyone else is firmly in the seats they paid for.
This can be amazing to watch in practice, where on a long haul flight you can see the person driving the plane welcoming their family into their seats, and explaining how everything works, while around them people wonder why they paid so much for their seats. Turkish Airlines cabin crew are particularly hot on self upgraders - those who sit in a seat different from the one they are assigned. Occasionally you can see people try it on, particularly from economy to comfort class, and they are always firmly escorted to the back. The only exception is if you have a definite problem with your seat in economy, such as with your seatback TV not working, where you can sometimes complain to the crew and if you specifically asked to be moved (slightly) further forward to Premium Economy (Comfort Class) and ask for this class by name, you may get lucky. If you plan to do this, make sure you do it before the meal service: when the trolleys are out, there's no moving about.
In reality, getting upgraded to business class on Turkish Airlines is nowhere as easy as even on European airlines. The airline has the Western, rather than American, model for upgrades longhaul. Which is to say you'll only get an upgrade if your paid for class is full, and then upgrades are processed accordingly to a pecking order of elite frequent flyer status. You are very unlikely to ever get an upgrade unless you are at least a Gold Star Alliance member.
To start with, make sure you are a frequent flyer, and you do fly frequently: after all, if Turkish Airlines are going to upgrade anyone, they will upgrade those passengers who fly with them pretty regularly, and hence will enjoy the upgrade enough to put more business Turkish Airlines's way. Then if the flight is full in economy, and someone needs to be moved up, the check in staff will first look at Diamond Turkish Airlines members, and then Plantinum level, and then at other Star Alliance members at the equivalent levels (Gold, and then Silver. Another thing that Turkish Airlines look at is how much you paid for your ticket: it's much more likely to happen with a full fare ticket (although occasionally you can get lucky with a discounted economy ticket).
As always, my advice on dressing properly in the pages on how to get an upgrade applies.