Current win-rate in Legend:
There are 2 types of hand you can start with using this deck. One of the hands is a more beast oriented hand, which generally consists of cards like Alleycat, Crackling Razormaw, Kindly Grandmother, or Animal Companion. The other type of hand is a more secret-oriented hand. You only EVER keep a secret if you have something like Secretkeeper, Eaglehorn Bow, and an early game beast like Kindly Grandmother or Alleycat. Otherwise it's just too slow to keep a secret in your opening hand. The main things you want to mulligan for are as follows (and are in order of greatest priority to least):
With one good secret:
With no secrets:
You really only keep bow if it's a tempo based matchup, like shamans and other hunters. Otherwise the keep is usually too slow unless you have a secret-oriented hand and can capitalize on the buffs to the weapon's durability. Also note that there is almost never a time that you keep Rexxar in your opening hand, try to go fast, don't go so slow!
Your aim with this deck is to kill your opponent by turns 5-6, and if you can't you want to use your Trackings to find your Deathstalker Rexxar to help sustain you into the lategame. The focus is usually on finding the strong early beast curve and using the secrets to help fill the curve in the later game with the Rexxar hero power. Look for every opportunity to get face damage in without compromising your board to board clears, and don't switch to Rexxar if your opponent is extremely low on life and has no good way of healing himself/herself back up. Otherwise, play the Rexxar as early as possible and try to hero power every turn that you can.
Good luck and happy climbing!