well, build up them skills, son. alternate tightening/loosening left and right nuts, and get things to where you like em. then crank down.

to get good tension, all you need is tracknuts, a good 15mm wrench, and your own two hands.

to get excellent tension, maybe throw in a chain tensioner or two.

if either of these scenarios is not the case, you need to practice more, double check that all the surfaces are clean, and make sure to REALLY crank down on the nuts.

edit: oh, and just makin sure - although they look like the 3rd one from the left, are you sure they are, ie, that they have the built in floating washer?