I do one big string of rotation whenever I do cross.
Also, know the relative locations of cross pieces.
Like on white cross (with white on top), from left to right, cross colours are green, red, blue, and orange.
On white cross on D, from left to right, cross colours are red, green, orange, blue.
Example:
Say a scramble was....
D' B2 D2 F2 U' F2 D' B F' U B' D B' F2 R F2 D' B2.
Scramble with white/black on top and green in front.
Since I am an avid white cross user, I'll solve white cross.
Inspection:
I'd first notice the RU edge. Doing an R B here would solve that edge.
HOWEVER! I will continue inspecting. (Time: 1 second, at most)
I then notice the FD edge. This edge needs to go to UR to be solved, but using UF as a reference point, it needs to go to its relative location to the UF edge: UL. Doing an F L' F' would solve that edge.
HOWEVER! I will CONTINUE inspecting. (Time: 1 second, at most)
Then, I see the DL edge that, when an L2 is applied, would be solved. However, using the UF edge as a reference point, I'd need to do a D2 R2 or a U2 L2 to solve it.
HOWEVER! I will STILL CONTINUE INSPECTING. (Time: 1 second, at most)
Now, to plan the cross.
All of those setups (R B F L' F2 R F) make the cross a bit odd to solve.
Thus, since the RU edge needs to be solved in UF at the end, why not do it at the beginning?
Planned: R' F'.
You see, that'd move the FD edge to FR.
Planned: R.
Now the UF edge in the scramble has gone to LF. This needs to go to UB, so you can do either a U2 F or an L2 B' to solve.
The decision is made when the DL edge is noticed again. It can be solved with an L2.
This would then bring the LF edge to LB, to be solved with B'.
Planned: L2 B'.
There is nothing to AUF since we covered it already, after switching the reference point to the white-green edge.
Put it all together!
R' F' R L2 B'.
And that's the cross.
However, executing it is different.
The first three moves (R' F' R) I'd do as (x R' U' R x').
The 4th and 5th moves would then be executed as (x' L2 U').
Then an x' move gets the cross on D, and you're into F2L.
Altogether:
Inspection rotation: x.
Execution: R' U' R x2' L2 U' x'. This should be very smoothly executed!
The entire inspecting process should take 5-8 seconds, on average. This one took me just under 6.
Execution should be under three seconds. I did this in about two, I'd say.
EDIT: (Off topic: Oh wow, this F2L sucks.)