I have to attend a fairly big meeting soon, a first for me, and I need to get some new clothes. It's really on the more casual side of business casual, so I'm not really sure what to even look at. I usually wear a polo shirt, jeans and canvas shoes (all black) to work every day, and I'm aiming to be only slightly dressier than that.
Any suggestions for shoes/shirts/pants?
Depends on how much you want to spend. At the very least, upgrade the pants to slacks or khakis. The next step up is what JonEdanger described, which will look classy but shouldn't upstage anyone if business casual is the standard.
For slacks, I bought a couple pairs of Dickies work pants: dressy enough for business casual but work-quality so they should last. My belts came from Filsons (cheap leather belts are just that: cheap. You want bridle leather and vegetable dye). My shoes are Sketchers Alley Cats: nice leather, not real expensive. Shirts are the least important part: a Wal-Mart long sleve will work fine, if it's pressed. You can iron the shirts and pants yourself and save some money (check out YouTube videos if you've never done it before).
And even after the washer and dryer, professionally pressed clothes are easier to re-press, not just in terms of a remembered ideal, but something of the crease usually remains.
If in doubt, fail on the dressier side.