So before shopping I visualize what I want as exactly as possible. I try to identify color, shape, material, with most wanted and 'also acceptable' options. I also try to be clear what I'm not looking for:
So for example, with some random preferences added --
summer topper - blazer, also possible - other structured jacket, not looking for: cardigan
colors -- powder blue, also possible - blush or cream. Solid or very subtle stripe or tweed.
shape -- hip length, low stance, nipped waist vs. boxy, different lapel styles fine as long as they work with both collared and no collar tops.
material - linen, cotton, or silk with man-made blends is fine.
price range -- ballpark this based on budget and projected frequency of wear.
I also review what I already have in this category so I don't accidentally duplicate.
When I have a clear mental image then I go into a store and look first for item type and then for color and then for size (depending on how the store is laid out).
I don't get sidetracked by cardigans (already have plenty), don't look at dark colors or bold patterns, immediately dismiss anything not the right length to wear with the clothes I'm wanting a topper for. I also try to wear the outfit I specifically need a topper for while shopping, so try-ons are easy. If there is nothing in the sections that have jackets (I check clearance too), then I move on to the next list item or leave the store.
Having a specific color or two in mind is key for me as it makes it easy to scan racks from a distance or super quickly as well, without needing to leaf through piece by piece.
This assumes I'd rather go to several stores for the 'right' item then spend time trying to find something I can make work, but that isn't quite right, at one store.
If there is something that fits all of this 'general' criteria, then (and only then) I look at details -- the brand, washing instructions, construction, fit, etc. If it seems largely promising and returns are hassle free, I take it home for additional try-ons.
I think of it as if I'm in a forest, and I want to mentally gray out everything but the raspberries, it's all just background visual noise that I can tune out. I don't approach or handle other plants unless I've already found the berries or am about to leave the berry-less store and have five minutes for random browsing.