Hi,
I have been experimenting with selection in the last 3 AIMCATs. I feel selection is really crucial in RC, DI and LR, because here you can end up losing not only marks but precious minutes which is irretrievable, that is in case you don't select the right ones. Initially, it was kind of difficult, but with trial and error, I have zeroed in on my strengths and am able to attempt consistent number of questions. For these two sections, I take roughly about 2 minutes per section to identify good sets/passages. In my opinion, better spend a minute or two in selecting the right RC/DI set; else one might end up spending even more time on individual questions in a wrong RC/DI.
For quants, I do not keep separate time frame for selection, but rather go through one liners first and take instantaneous decisions whether or not to attempt them; I am yet to cross the cutoffs

in quant. Needless to say, I am still working on quant strategy.
-pooran