You’ve got Wikipedia, the free encyclopedia, and then there’s Wiktionary, the free dictionary. What’s great about both of these tools is that they’re free and available in different languages. You can look up Russian words on Wiktionary and get a translation…but that’s not it! You can also get declension tables, etymology, and more (for select words)! If you’re not using Wiktionary, you should definitely start!
When you look up standard dictionary forms like “идти” or “мужчина” you’ll usually be taken right to what you’re looking for. Once you get there you get one or several English translations, and then the inflection that the word takes. Most words have stress marks, and some even have IPA or audio pronunciations.
If you’re really lucky, you’ll even get to see the word in use.
However, if you look up an inflected form like “идёт” you’re probably going to be taken to the search page, in which you can find the page that will point you to the right direction.
Sometimes you have to be careful, though. Wiktionary is just like Wikipedia — anyone can edit it. That means you always take a slight risk. What you’re seeing could be wrong. But just like Wikipedia, Wiktionary has administrators that monitor what users edit and add to the site.
So if you’re not already using Wiktionary, you should give it a try once in a while. It’s often much quicker than opening up a dictionary.