Instructions
Log in to the TPPC forums a few days before one of the Golden Days, which fall on August 2nd, December 25th and January 1st each year. Shrimpy, the creator of TPPC will post a riddle that will tell you how to get that days Golden Pokemon.
Solve the riddle to learn three different Pokemon and three different items. There will be a riddle for each of your three Pokemon slots in the game. When you have solved the riddle, you will know which Pokemon to equip in each slot and which items to give them.
Log into your TPPC account on the Golden Day and equip the three Pokemon, each with the correct item and in the correct slot. Click "Evolution Gym" from the list of links on the left side of the page.
Battle through the evolution gym with your team of Pokemon. When you have won all of the battles, the Pokemon in slot one will evolve and turn gold. You are now the proud owner of a rare Golden Pokemon.