Quoted just 'cause I totally agree.Ben Nielson wrote:Then, ditch anything that has romaji in it. It's basically just robbing you of more hiragana/katakana reading practice. The sooner you take away the romaji crutch, the better off you'll be.

You could try and come up with a visual thing to distinguish them... to me, マ is more like 'A' because the corner is at the top, and 'ム' is more like U because the corner is at the bottom.This all said, I still have to stop and think when I want to write マ and ム. Not sure why, but those two are going to plague me forever.
Otherwise, I'd suggest finding a way to use them as much as you can (use a guy called マーク and ベトナム in all your examples or something), I had so much trouble with シ and ツ at first, but I ended up using ッ so much (especially since I write my name with it) that I have no problems with them anymore.