OPK Newbie! Tips? Advice!

Jennifer
After losing our first pregnancy, D&C and two cycles later I'm going to try Clearblue Digital OPKs this cycle. The instructions claim to start testing based on -20 days from expected period but I read some other posts referring me to follow "sperm meets egg" program which says to start testing on cycle day 8. Have any of you ladies had success with either of these routes for TTC?