I don't manually drop the QB back, that way there's a much better chance that his feet are set for the throw...
1) Pre snap read...probably motion one WR to determine Man or Zone, get a feel for what side the blitz may or may not be coming from...
2) Based on step 1, choose a side of the field to focus on and the D player the is my "read" for the play as a result...
3) After the snap take a nano second to determine if the LBs are blitzing or dropping back into coverage as well as the DBs...
4) If it's an obvious blitz, throw to the receiver who is likely to be left uncovered by the vacancy of that area by the blitzing defender...
5) If they drop into coverage, look at the side of the field I chose in my presnap read, deepest route first, intermediate second, checkdown in the flat last...
6) Throw to the first guy in that progression that is wide open, "winning" his route or is about to gain a step on his defender or is about to make a break or cut that the coverage looks unlikely to mirror...
7) Light tap to float one, medium tap for most, hard tap to gun it, depending on the above...
8) Complete steps 3 through 7 in under 2.5 to 3 seconds...
9) Hope for the best...
I hope this helps, I'm no trained IRL QB, but have decent knowledge of football and a lot of football gaming experience...this is the first time I actually thought this much about how / why I do it how I do, but it works quite well and realistically...
Just like the IRL guys, you have to "feel" the rush...don't waste a half second or more actually looking...
Have fun and good luck!