Welding Tips and Tricks

i have a new test coming up it is a naval gmaw unlimited xray horisonal vert and overhead on alumnium they have tested about sixty people and all but five have busted out does anyone have any tips for me i have welded on alumnium at shipyards for about a year and passed several ut's but gotta say they wont even let most people that i know that i worked with that are good welders get past visual they are being really picky if any one has ever taken and passed a naval cert on aluminum and has any pointers i would really apricate it