How to change daily surprise offer:
Green_Shade, mkell_226, Laulajatar, Huff, & f_alcon have posted about this, but for anyone struggling, here's a simple step-by-step guide to how I've been doing it (using Chrome, but the process should be similar with Firefox or IE).
1. Open
http://www.gog.com/forum/general/daily_personal_deals_tracker_2013_drmfree_winter_sale/post1.
2. Open
http://www.gog.com/ in a second tab but do not login.
3. Examine the three daily surprises. Check the tracker thread to learn the discounts. Login if you want to purchase one of them; otherwise proceed to the next step.
4. Press Ctrl+Shift+Delete. Make sure the option to delete cookies is selected. Press the button to clear browsing data.
5. Go back to the GOG.com tab. Press F5 or the reload button to refresh the page. Go to step 3.
Repeat until you find a daily surprise you'd like to purchase.