I don't agree with TATY that accent is mainly affected by vowels...I beleive there's a bunch of problems like palatalization..well vowels of course (mostly in a way that there's no opposition of long and short vowels in Russian...well yes sometimes the sounds really different
), sound clusters,sounds that don't exists in English language...but what I really put on the top of it is consonants..not vowels...I already mentioned that in audio lounge...I mean I can really imitate American(for instance) accent doing the vowels pretty ok but still making it awful...So to say it roughly I think it's all about consonants (the secong place takes consonant+vowel clusters...well that's palatalization I'm talking about)
Just a quick example:
Let's take a russian word "томик" and an english one "atomic". Drop the [a] sound in the word "atomic" and now we got two similarly sounding words. To make tomic sound like томик one shouldn't aspirate the [t] sound and make it dental instead of alveolar, make [м] sound palatalized and lose the aspiration (and maybe even the palatalization) articulating the[k] sound. The last two points are maybe not that clear in this exapmle (it just came from the top of my head right now...sorry
) however I often notice big problems with that stuff...it can be more clear if we compare words like:1. пень-pen ([п] sound should be palatalized and shouldn't be aspirated...at least that strong as they do it in english)