Rogue builds are often dictated by the highest dps weapons they have available to them, so simply going down one tree on friends' advice is a poor way to build your DPS in the long run. With Daggers you are only supposed to use one of two CP builders, Backstab or Mutilate. Sinister Strike is awful with daggers.
Combat at 71 is a very easy style to play when you can get your hands on decent fists, which happen to drop in the first two dungeons of WotLK.
Respec to this:
Talent Calculator - World of Warcraft
And put the rest of your points into the tree to 80 like this:
Talent Calculator - World of Warcraft
Cycles are dead simple. Sinister Strike to 5 CP, SnD, Rupture at 5 CP,
Eviscerate if you have more than 4 CP, Rupture is ticking and you have more than ~10 seconds left on SnD. From there it's just learning how to time your CDs like Blade Flurry/AR and clicky trinkets, which is all dependent on the fight.
If you want to keep using daggers I can post a Mutilate build, but I can't speak to its effectiveness at 71 since I was combat swords at 71.