There are many different ways that work for different types of players but the ones that I have seen work the best are.
1.Going into the diner near the spawn and taking both sentry guns and using it to cover the diner by putting them behind the counter and letting the Russian's enter through the front door and firing away while placing claymores at the back entrance. It works even better with a partner because it allows you to cover the different entrances and have up to four weapons firing including the sentry guns.
2.A more risky but rewarding one is to attempt to rush to the crashed Pave Low near the sports bar and the bank across the street from the spawn. This is a good spot because the Russian's can only enter through the open tail and it is very easy to place a sentry gun and cover the back while you snipe out of the different windows. However the only downside is that the BTR-80 and the Mi-28 Havoc still have to be dealt with after the soldier's have been killed but usually you can rush to the different buildings and grab a rocket launcher.
3. The Russian UAV that fires predator missiles after round two can actually be very useful in that running briefly outside will cause it to fire missiles in your direction which more often than not will cause the missiles to strike Russian soldiers by accident and kill them which can be useful for thinning out attacking groups if you feel overwhelmed. I wouldn't try this on the BTR-80 as it moves and will cut you down before you can get close.