For starters, here is a map of Otaniemi, with all party locations and bus stops shown.
For a really good map, take at look at this map courtesy of the City of Helsinki. Also check out their address locator.
Parking: There is no parking right next to Rantsu. Leave your car in the Smökki parking lot and walk.
Public transport: Use Smökki's buses. Once you get to the last stop, turn left onto Jämeräntaival and walk past three groups of houses. The last of these is JMT 5, turn right after it and walk down the path past the houses (we'll put a sign and arrow here). The path ends in a T-crossing, take the left fork and the house you see in front of you, half-buried in the hill, is Rantsu.
Parking: There is a large free parking lot right next to Smökki, so it's no problem.
Public transport: Espoo buses 2, 4(T), 10, 15 and YTV buses 102(T), 501T and 502 all go directly to Smökki, just get off at the last stop and head for the top of the hill. The best option for most people is 102 which leaves from Helsinki's Linja-autoasema (platform 51). The last bus from Helsinki leaves at 01.50 Fridays and 01.20 Saturdays, and the first one in the morning from Otaniemi goes at 06.45 Saturday, 07.00 Sunday. You can also take 103, 194, 195 or 505 but you will have to walk a few hundred meters from the Kemisti stop.
Parking: There is a parking lot hidden behind TF. If there's no space there, use Smökki's parking lot.
Public transport: Use Smökki's buses. Once you get to the last stop, keep walking forward along Otakaari past the crossing with Jämeräntaival (to the left). After the crossing, the third house on your left (a big concrete thing shaped like a triangle) is TF, as the big blue sign says.
The main entrance to TF is at the tip of the triangle, away from the direction you are coming from. The Luola entrance is a little stairway leading down from the other end of the triangle.
Parking: There is a parking lot hidden behind TF. If there's no space there, use Smökki's parking lot.
The main entrance is on the right side of the building (Otakaari 20),
in the cellar down the lane marked "Rehtorinkuja".
Parking: See OUBS.
The entrance is immediately on your right as you enter the courtyard, down a short flight of stairs.