Leningrad Oblast is most often visited by travelers staying in Saint Petersburg, either daytripping or overnighting to places of interest. If you are interested in Russian history or Orthodox art, you should put Staraya Ladoga at the top of your destination list, but be aware that it is difficult to get to on your own and a tour would be invaluable. If castles are your thing, Vyborg, Shlisselburg, and Ivangorod are excellent destinations, but in the case of the latter, be sure to get all your paperwork in order because the Estonian side of the city is more interesting and accommodating. And if Saint Petersburg and its suburbs haven't tired you out of seeing palaces, Gatchina's is quite impressive.
As a general rule, the closer you are to either a major tourist site or to Saint Petersburg, the more likely you will find people who speak English or other European languages, like German, Finnish, or French. But some knowledge of Russian or a qualified guide will almost certainly elevate your experience here.
The main border crossings are at Narva/Ivangorod for Estonia and along the main Helsinki–Vyborg highway for Finland. For the Russians especially, triple check that your papers are in order.
Most visitors to the region arrive via Saint Petersburg's airport or rail terminals.
In general, the most efficient and cheapest mode of transport is to take electric rail (eh-lehk-TREECH-ka) services from Saint Petersburg's main rail terminals. Tickets are very cheap and the electrichki will take you to all but the smallest destinations in the region (Staraya Ladoga).
Saint Petersburg beers predominate in this region, and that's a good thing. Go for a light Baltika #7 or a dark Baltika #8.
The whole of Northwestern Russia and major cities across all Russia await from the rail stations and airports of Saint Petersburg. The region is also a convenient last stop in Russia for travelers heading on to the Baltic states, Finland, or Belarus.