I've been trying to practice daily for the last few weeks (took last week off, oops), noticed a couple of things, for better or worse. If I know it's all numbers, I can copy quite well. I listen for the number of dah's and I'm good. However I noticed while copying some random callsigns this morning that I would confuse say 7 and Z, 4 and V. I don't know how to listen for even/odd characteristics in the character, like what I vs S vs H vs 5 is. I and H are even, S and 5 are odd; but for me to hear to that I practically have to count dits. S and H sound really the same unless if I really concentrate. Sending s and h for me is rough too, on my keyer, at 13wpm I have a rough time sending h's and 5's. winds up being a random number of dits (and if I just send one dit at a time I destroy the spacing). Moving on, I do find at even 20wpm I can get a mental snapshot of the character just sent, and will replay it. Unfortunately while I'm relistening to the charcter, trying to determine if it was W or J, I usually miss the next character. I really need to learn to just skip characters I don't hear and immediately recognize. Finally, if a word has some E's and I's I tend to blow the word, as I can't write 'em fast enough. An E or I followed by something I don't recognize real well (like V) and I might as well stop.