Fast what needs to get fixed the most in your life.  Fasting and prayer brings your body into submission to the spirit.  Don't forget to pray!
Gal 5:25 If we live in the Spirit, let us also walk in the Spirit.
Gal 5:16 I say then: Walk in the Spirit, and you shall not fulfill the lust of the flesh.
Rom 8:14 For as many as are led by the Spirit of God, these are sons of God.

Let us know how its going during the fast.  Testimonies, prayer request, words of encouragement