I pay attention to the neckline of any top I put under a jacket and how it works with the jacket. In general I steer away from shirts with collars as I find them too fussy underneath a jacket/ adding bulk around my neck/shoulder line, but I do love the look on others -- especially those with longer necks and more delicate shoulders. I also don't wear turtlenecks because they look awful on me, but love the t-neck+blazer look on others. I tend to prefer scoop necks or crews that aren't too high (need to elongate the short neck). For some reason V-necks are a bit trickier, but not sure why.
I wear my tops untucked, and generally prefer a flowy, tummy forgiving, loose blouse underneath, with the jacket carving out the appearance of a waist and adding structure. Sometimes I'll go with the "high-low" effect with a shorter/cropped jacket over a longer tunic. Sometimes I'll go with a looser, longer boyfriend-style jacket over a more form fitting outfit underneath.
I do often wear jewelry to fill in the neckline. It can range from a statement necklace, to something more delicate and subtle (lately I've been going in the latter direction). And sometimes a pendant looks just right, provided I'm not planning on buttoning my jacket, or the jacket has no buttons to close.
I also LOVE to scrunch/ roll my jacket sleeves! Bonus points for jackets that have interesting linings at the cuff, and that will stay up in scrunched mode. Sometimes I'll scrunch the jacket sleeves, but still pull the blouse sleeves all the way down to show, especially if they're interesting (pattern, cuff detail). Or flip the cuffs up over the scrunched sleeves.
For customer-facing / important days (like giving a preso), I'll do the suit-like matchy-matchy look, such as black jacket with black pants, or navy jacket over navy sheath dress. I then introduce some pattern for interest somewhere -- if not a blouse, then fun patterned shoes.
If I'm wearing a darker jacket, I find I need something white near my face, so very often my top of choice will be white as it lights up my face. With lighter jackets that have more going on (pattern, tweed) I do like the column of color approach. Let's just say I get a TON of use out of two simple scoop neck shells, one white and one black.
For work the top tends to be a blouse or shell in silky type material. For casual it could be a tee shirt or sweater. And for casual I'm much more likely to swap the pants out for jeans.
