On the top picture on this page: the middle part looks the best. From this view it seems concave, try adding more filler or slowing down. 3/32 filler will work, 1/8th is easier for me. Slow down and get the puddle going good, step forward with the torch, dip the wire, then step back to burn it in. Don't be afraid to manipulate the torch to get it to burn in how you want to as well. As long as your not over-filling you shouldn't have penetration problems, if the amperage is high enough and there are no defects in the weld. TIG is the hardest to learn because of the seperation of filler and penetration, with MIG you have them both happening at the same time. TIG you have all the control in the world. Keep a steady, consistant torch angle, consistant speed and consistant puddle size and step. Step, dip, step back, step, dip. step back. Rinse and repeat.