In Russian, in the nominative case, you make a plural by using the letters "и", "ы", "я" or "а".
For masculine nouns:
If the word ends in a consonant, add “ы”.
Replace “й” with “и”
Replace “ь” with “и”
For feminine nouns:
Replace “я” with “и”
Replace “ь” with “и”
Replace “а” with “ы” (unless previous consonant is Г, К, Х, Ж, Ч, Ш, Щ then replace with "и" as per the spelling rules.)
For neuter nouns:
Replace “о” with “а”
Replace “е” with “я” (don't forget the spelling rules)
Some examples:
студент (student) - студенты (students)
газета (newspaper) - газеты (newspapers)
здание (building) - здания (buildings)
More information you can read here: http://speak-russian.cie.ru/time_new/eng/grammar/
