Getting to Highgate by public transport is recommended, as parking is very limited around the village. Trust me, its just not worth it unless you plan to park somewhere further afield. And if you do, beware of the Controlled Parking Zones!
Highgate is accessed via the Northern Line; you can either get off at Highgate (which is nowhere near Highgate Village) and walk up Southwood Lane which should take you approx 15 minutes or at Archway (which is also some distance but has bus links). Check the service on the Northern Line by clicking the tube sign on the right, and give yourself plenty of time as there are often delays.
From Archway tube station, exit via the signs for Highgate Hill, and take a 143, 210 or 271 to Highgate Village. You could also walk up Highgate Hill, past the Whittington Stone, and take the turning on your left into Waterlow Park.
This affords a less strenuous ascent and takes you past Lauderdale House and onto Swains Lane should you wish to visit Highgate Cemetery. The cemetery have excellent directions to Highgate on their website which you can read here. DO make sure you check the availability of places on guided tours if you plan to visit Highgate Cemetery West, to avoid disappointment!