Basically, when you have no clue, you want to use practice to get an idea of how long the pattern is and where the friction/hold area is.
Best thing to do is on your very first couple shots, just kind of set the ball on the lane, literally at about 50% speed, and watch how far down lane it reads. This will give you an immediate idea of whether you'll more than likely need to play an inside line(for longer patterns) or outside line(for shorter patterns).
From there you'll then want to then try to find the oil/friction line in the pattern. Easiest way is to start at 5 and play straight up it, then move in 5 board moves.
The biggest thing from the start though is just finding the right angle of attack.