[QUOTE=oregonism;631354]I went out on one of the local flats for the first time this morning, but saw very little. I was out right at sunrise, and the low light made it really tough to see anything."
Early sight fishing on salt flats is difficult
unless you have really calm water, a light colored bottom and active fish. Slow moving, cruising, fish are hard to spot then. First consider the polarization of your glasses. Polarization is most effective when the sun angle is from 30 to 60 degrees.
Lower angles at dusk and dawn renders polarization ineffective. The same applies around noon as the sun climbs to 60 degrees and higher. It's then you have to rely on other ways of spotting fish. First of all you can always use contrast
and the color lens for max contrast is yellow. Get a pair of light yellow for those early and late hours and they'll work great on overcast days also. Secondly you need less tint, hence the "light yellow," instead of a heavy or bright yellow. I found a pair of Hobies light yellow that are super in low light or early/late.
For that mid day sun you need much darker sunglasses and neutral dark grey or dark green are best all around and it's here that mirrored lens, pioneered by Bushnell in it's Ray Bans excel as the mirror adds a bit more blockage.
Unfortunately the grey/green colors aren't best for most saltwater flats and the edge there goes to a darker brown or amber. This is due to the bottom coloration (sand and grasses, or shades of brown, a little green and tan) primarily and the fishes color on a secondary note. (most are fairly silver and therefore reflective) I've noticed that Costas is coming on strong with mirrored lenses these days.
I'm not addressing the part ones experience plays as the folks herein did an admirable job on that but rather prefer sticking to knowing your glasses and uses. You asked, "Is there a trick to spotting bones on grassier flats? Should I wait until the sun is higher in the sky? Pretty much all my fishing will be over grass, so tips would be greatly appreciated!"
Visual acuity, so get a prescription lens if you need it, is primary, and yes the best sight fishing will be late morning due to the polarization angle and again at mid afternoon. Since bones are the original mirror blind fish, you are looking for lines, wakes, waves, disturbances, etc. Their silvery sides reflect the bottom between you and them hence the mirror blind I mentioned and which is now gaining popularity among hunters. It's here that mix of yellow and brown or amber works miracles as the yellow enhances the contrasts that will enable you to pick up the fishes silhouette/and barred lines. The brown part of that yellow helps with seeing things against a brownish/green/tan bottom.
All in all if I had but one pair it would be my brownish yellow or amber, glass lens, Action Optics glasses. I do have the Hobies mentioned above and another pair of Smith AO's in neutral green/grey for the brightest sun.
Have to admit though that Ray Ban nailed it many years back with their gradient, mirrored, polarized glasses for water work. The gradient was double, top and bottom a very dark tint and neutral colored fading to a lighter tint in the middle and back to very dark on the bottom thereby stopping not only the direct rays but the reflected rays also. Wish I had a pair today.
Those neutral AOs are my stream and river fishing glasses also during the heat of the day as they do help with sorting out fish from all the reflected greens of the forest and fields.
Other than this experience will come and so will your bones. Get good glasses, and make sure the top, bottom and sides are well shielded, ie side shields and good wide brimmed hat as lights coming in here will hinder
your spotting greatly.