Ranmore Common has a few runs.
Probably the obvious thing to do is go on one of the Nirvan Sunday runs.
Else (probably a bit contentious giving directions, but…)
If you are going up Ranmore Rd from Dorking to Ranmore Common Rd, near the top, on the rhs is a 5 bar gate. Either sling your bike over, and ride back under the road, or look for a gap in the hedge on the lhs of the road. It shouldn’t be difficult to find the start of two runs- Grievous Angel is the second I think, I’m not sure what the first one is called.
Warning: I have a broken arm from coming up short on the bigger gap jump on the first run (the one which starts with a drop over a downed tree trunk.
The other lines I know of are on White Down Rd- from the A25 direction, across the railway bridge on the there’s a kink in the road as it starts to go up- on the rhs if you explore up the hill close to and parallel to the road you’ll find the stuff that’s been built – there’s an old pillbox a bit up to drop off, some bombholes, drops, jumps and gaps. Some more riding on the other side of the road too.