Although the central part of Saint-Petersburg looks like a European city, unfortunately, it is not as compact as many cities in Europe are and, most likely, you'll need to use public transportation.
This page is not a complete guide or reference. The options and routes listed here are the easiest to use but not necessarily the most efficient. Many of inhabitants prefer minibuses as the most flexible and convenient kind of public transport. However, it would be too complex to explain all details here.
First and the most important recommendation is: do not use any cars inside the central part of the city if you do not have luggage or other special reason to do so. Due to traffic jams, the travel time might be unpredictable. Of course, most likely you'll use a taxi cab to reach the airport.
The subway (metro) is reliable but not well developed. If your hotel is in the central part of the city, you'll need only few stations, all located on line 3.
For all types of public transport (except taxi) the payment model is 'per trip'. There are no time-based tickets (like hour, day etc.) In metro, the trip starts when you enter the station and ends when you exit, no matter how many times you change lines or how many stops you ride.
For other kinds of transport, the trip starts when you enter the vehicle and ends when you leave it, no matter how many stops you ride on the same vehicle.
The cost of one trip is currently 20 RUR. You have to buy either a token (for each trip), or a smart card which may be pre-loaded for several trips. If you are buying trips on a smart card, you have to deposit 30 RUR for the card, in addition to the cost of trips and you can return the card to the ticket office and get your deposit back (as 30 RUR is currently less than 1 USD, you probably are not really interested.) There are several multi-trip ticketswhich can be loaded on the card. The most practical are 10-ride ticket valid for 7 days, 20-ride valid for 15 days, or flexible (load number of rides between 2 and 60, valid for 90 days). The 10-ride and 20-ride tickets have discounted prices 165 RUR and 315 RUR, respectively. When all trips are used, you can load the card again (not necessarily same type of the ticket), with flexible load you can add trips at any time.
The ticket office is called 'kassa' (in Cyrillic looks like KACCA). There are automatic machines issuing smart cards but they operate in Russian only. You might want to print this bilingual page and show appropriate part of it in the ticket office. The page contains requests for 1 token, 2 tokens, 10-ride card, load of 17 rides to flexible card, and 'put the number of rides yourself' for flexible ticket.
For all other types of public transportation (buses, trolleybuses, and trams) you need cash. The cost of one trip is 18 RUR. There is a conductor selling tickets in any vehicle.
The mini-bus service has a pre-defined rout (like a bus) but can stop anywhere (like a taxi). The cost of a trip depends on the route and ranges from 20 to 50 RUR. The payment method is always cash (paid to the driver). The price is always posted on the door or inside the vehicle and is not a subject of negotiation. On long routes, the price may depend on the distance. Most of the drivers do not speak English and some of them do not speak Russian either. Minibuses are widely used by locals, but most likely you will not need to use this services too often.
During the conference your favorite transportation will be a trolleybus (electrical bus moving along wires). As soon as you are on the main street (called 'Nevsky prospect'), trolleybus is the most practical kind of public transportation. (They have dedicated lanes and are less affected by traffic jams.) Your routes will be 10 and 11. There are many other options not mentioned here.
DO not accept offers from taxi drivers in the arrival hall or outside the airport. These taxi are safe but unreasonably expensive.
Please note that terminals of Saint-Petersburg airport are not connected and you must know your departure terminal in advance. Most of international flights are from terminal 2, but there are some exceptions.
Probably the easiest method is to preorder taxi from the hotel or from Monomax agency. Alternatively, you can take a bus or minibus from metro station 'Moskovskaya'.
If your hotel is located on 'Bolshaya Morskaya", you can cross the Palace square, the Neva river, and you're done. If, for any reason (too cold, too windy, etc.) you would like to use public transportation, follow the instructions below.
If you are on the 'Nevsky prospect", take a trolleybus #10 or #11 in the North-West direction, exit on the first or second stop after the Neva river. The river is approx. 400 meters wide, there are 3 small rivers crossing Nevsky prospect, see the map. This is applicable, for example, if your hotel is 'Oktyabr'skaya'.
The Nevsky prospect goes from North-West to South-East, so the right direction is that of decreasing building numbers. To take the trolleybus in the right direction, you must be on the street side with even numbers.
From any other place, use metro to reach Nevsky prospect (stations located on the Nevsky prospect are called 'Nevsky prospect', 'Gostiny Dvor', 'Mayakovskaya', and 'Ploschad' Vosstania').
If you would like to explore the city, you can reach the conference venue from 'Vasileostrovskaya' metro station (15-minute walk). Exit from the station, turn right twice and go to South in pedestrian area (lines 6-7, see explanation of line numbering below). When you reach the river, turn left and proceed until you reach the conference venue. This is the easiest to explain but not the shortest path. There are several alternatives, see the map.
The workshop venue is different from the main conference venue.
To reach the workshop venue, use metro and exit at 'Vasileostrovskaya' station (line 3). When you exit to the street, turn left and go straight (along tram tracks) for 4 blocks until you reach the street called '14th line', turn left and continue until you reach the building #29. There are big letters MAT-MEX above the entrance. (Actually the letters are Cyrillic, but these are same as Latin except X which is close to Latin H. The meaning is MAThematics and MECHanics)
Note that in this part of the city the streets have unusual naming: each street going from south to north is considered as two lines. So, 8 and 9, 10 and 11, 12 and 13 are actually sides of 3 streets which you have to cross when moving from metro to the workshop venue. The numbering starts from 0, but line 0 have a name.
From the conference venue, just cross the river (walk or one stop on trolleybus #10 or # 11).
From Nevsky prospect - no need to cross the river twice.
The entrance to the Museum is from South (from the Palace Square).
The reception will take place in 'The House of Scientists', formerly a Palace of Great Duke Vladimir. It is located on the Neva embankment to the East of the Hermitage. The Hermitage is on the South side of the river, this should help to take right direction.