To advance to Hawkeye, you must collect 3 marks.
The Mark of the Seeker is reserved for those who pass the Trial of the Seeker. You must be above level 35 to qualify. To take this trial visit Master Dufner of the Town of Giran.
The Mark of Trust is reserved for those who pass the Testimony of Trust. You must be above level 37 to qualify. To take this test visit High Priest Hollint at the Town of Oren.
And last, the Mark of the Sagittarius is reserved for those who pass the Test of the Sagittarius. You must be above level 39 to qualify. To take this test visit Guild President Bernard at the Hunters Village.