Bed Cred is like having street cred but in the sack. For instance if you pull off a high skill or high risk maneuver such as the shocker, the rear admiral, a threesome or a white sanchez then you've earned some bed cred. Bed cred can also be earned by going above and beyond to please the other partner(s) involved.
Hey man check it, I was with this girl last night and I gave her the shocker and 3 orgasms!
Nice man. I'd say you just earned a healthy chunk of bed cred.