One of my favorite quoted expression is: "By failing to prepare, you are preparing to fail." (Benjamin Franklin - 1706-1790) But there are also many variants, that are 'close' to swindle practices, but not (yet) labeled as real illegal organizations.
These are organizations that will use methods to keep you as long as possible as a paid customer, or those who ask far too much money for their services.
Ask specific questions and check if you receive answers on these questions In case you are using an Agency with email forwarding or other mail-services, and your correspondent is not responding on your specific personal questions, this could be a sign of being suspicious.
To be very serious in your intentions and to be very open to her, gives you a response which you can analyze as reliable or not.
Important is to see how your mutual correspondence is developing, about what kind of subjects you both are talking.
But if the woman starts (in an early state) with questions concerning money, for any kind of reason, than you have to be careful and you have to analyze if these questions has anything to do with the situation you and your correspondent are aware of.
You can also first visit our recommended agencies that you can find in this topic.
Write a detailed introduction letter (preferable translated in Russian), to receive a detailed reply of the woman If you write your Russian lady for the first (introduction letter) time, please write a detailed letter about yourself.