BBT questions

Janet • 37 year old Married Mother of 3 Sons 19,17 and 13 TTC 2 yrs for Baby #4 after Tubal Reversal.
It's my first month charting my bbt and I really don't know what to look for. Today I'm 12 dpo and my temp went to 97.38 My question is should my temp go up right before my exspected period and is that a good or bad thing for hoping is a pregnancy?