Anyone who has lived in Russia for a while can tell you that Russian superstitions are vast and intricate, and Russians take them far more seriously than Westerners do. While some Russian superstitions are similar to those found in the west, many of them, you will find, are new and surprising. It pays to know about Russian superstitions when traveling to the country. Not only will you avoid possible cultural gaffes, but Russians will respect that you have taken the time to get to know their culture and their traditions. Most Russian superstitions are followed throughout the countries of the former Soviet Union, though other republics add their own to an already complex mix. Here's a good selection of the most common ones.
And finally--feel free to walk under all the ladders you like, and open umbrellas indoors. These are a few of the things that Russians are not superstitious about at all. Hopefully learning these folk beliefs will give you some insight into Russian culture. Here's another article for general tips on how to behave in Russia.