Locally, follow signs for A4180 (Bury Street / Duck's Hill Road) from A40, then turn onto the B469 (Reservoir Road). For fuller directions, or if you are coming from a long way away, I would suggest using the AA's Route Planner and enter your postcode and the Railway's postcode (HA4 7TY) in the relevent spaces.

Ruislip Station is served by both Piccadilly and Metropolitan line trains, and you can then get to Ruislip Lido either by the H13 'bus, which terminates next to the lido, or by the 331 'bus, which stops at the Six Bells pub, nearby the lido. Alternatively, you can go to West Ruislip Station (Chiltern and Central) and get a bus to Ruislip Station, then change to the 331 or H13 service to the Lido. All the stations and bus services mentioned are in travelcard zone 6.