One travel tip I have heard is to make sure your carry-on baggage enters the scanner before you walk through the metal detector. However, there are some TSA checkpoints where this is tricky to do. At LGA, for example, there are 3 rows of bins, arranged like so.

ROW 1 =>=>=> is the conveyor for bins to enter the scanner. This row is out of passengers' reach. A TSA officer watches over these bins.
ROW 2 ====== is enqueued for merging into Row 1, the same way cars zipper-merge from two lanes to one.
ROW 3 ====== is closest to you, the passenger. An empty tray bobs up from below, and you put your baggage in the tray and push it forward to Row 2.

I travel with only 1 carry-on, no personal item. When I push my single bin from Row 3 to Row 2, it is still in passengers' arms reach. So, I would ideally wait for the bin to make it to Row 1. However, a TSA officer said I was "good to go" as soon as I pushed my bin forward to Row 2.

In this setup which I have seen at other airports and not just LGA, do you insist on seeing your belongings make it to Row 1, where no other passengers can grab it, before you proceed to the metal detector?