How to Rebuild Trust in a relationship
1) To be trusting yourself
Have faith in yourself and your partner/spouse
2) Always be fair
Your partner has already chosen to commit himself/herself to you, there is no need to bring up the past at every chance you get. Try not to constantly judge your partner.
3) To be reliable
Show your partner that every thing you do from now on is an open book case, there are no excuses which have no rational explanation.
4) Be understanding (I know it is hard at this time)
There are times when your partner has an explanation however it does not compute with you, let's not take for granted that he/she is lying again. This creates stress and unwanted negativity.