I think there is a big diffrence between 100NL and 200NL, when I moved up I had to get used to that I couldnt limp in for cheap as much and see if I could trap someone with a hand like 79s. Another thing I notised was that I more often got reraised 4 times. When I raised $8 on the button I often got reraised to $27 from the BB, which I rarely did in 100NL.
From 200NL to 400NL I really didnt feel much diffrence, its quite the same pressure at the tables. I havent had many 600NL sessions because I dont think im good enough yet but I feel there is a diffrence again here. I see more speculative play here and more bluffs. People seems to love squeeze play here a lot so I have to tighten up even more at this level. Another thing I notised is that there is a lot more players with a big ego here that is influenced by their play because they think they are a world class player and therefore think they have to be creative all the time, so I really think ABC poker still works fine here, but im not experienced enough to tell more about this level, just what I think, others might disagree.

About bankroll management always keep 15 buy-ins for each level, so if you want to move up from $1-$2 to $2-$4 you need at least $6000 at your account. If you get down to $3000 because of a bad streak or whatever caused it move down no matter what. I have seen many players bust a bankroll because they move up and claim that they just were unlucky to hit a bad streak just when they were moving up, but it could also be a bad play. Just dont let any ego control you to make bad decisions.