As the problem -and fear- of scammers is such a big issue today, I had to make a section about scams all of its own. However, my first piece of advice is don't get obsessed with the idea that you are going to get scammed, this is about finding a wife.
You probably clicked on this tab because, unfortunately, today men like you are as worried about getting scammed as you are about finding the right lady. I do not think you should worry about getting ripped off every time you write a letter, receive a phone call, meet a girl, etc. After all, it is supposed to be an enjoyable experience and your efforts should be mainly concentrated on finding the right person and making the relationship work. Follow the advice that I give you here and that of the bodies and websites which specialize in collecting information on scammers. Even governments in countries like the USA have set up special advice, on dating scammers, in their websites.
You only need to search in Google "Foreign bride scam" to see that you get thousands of results, This shows the extent to which Western men worrying about getting ripped-off has grown. There is a proportion of men who are not marriage material, for these girls, and when they do not find what they want through the agencies (an 18 year old girl who looks like Christina Aguilera falling for them) they promptly go to the forums and say what a scam the agency -or lady- in question are.
Unfortunately, today you will do well to visit regularly the sites that collect reports on known scammers to check if any of the ladies (or fronts) you have got in touch with are listed. These sites did not exist when I was looking for a bride and I could easily have been scammed due to my lack of experience.