A good board is a pleasure to work and a poor one fights you at every step. Most of the difference is decided before you pick up a plane: by what you bought, how long you let it settle, and where it waited until you needed it.
Buy for the job, then let it rest
Look along each board for twist, cup and bow before you load it. Check the end grain: quartersawn stock, with growth rings running steeply across the end, moves far less than flatsawn. Avoid boards with the pith in them, because they almost always split.
Timber leaves the yard at one moisture content and your workshop sits at another. Bring it home, stand it in the space where it will be worked, and give it a fortnight before cutting anything to final size. A cheap pin meter tells you when it has settled.
Stack it so air can move
Never pile boards flat on one another. Lay them on stickers, thin dry battens spaced every forty centimetres or so, with each sticker directly above the one below. Air then reaches both faces evenly and the boards stay flat. Keep the bottom layer well off a concrete floor, and keep the whole stack a hand's width away from any outside wall.
When the store itself is damp
Boards stored in a basement or a closed garage sometimes come out with a grey bloom, a musty smell or dark spots that sanding cannot remove. A little surface bloom on fresh, wet timber is common and wipes away once it dries. Growth that keeps returning, or that also covers the wall and the joists above the stack, means the room is holding too much moisture for timber or tools. Readers with basement shops in the American Midwest have told us that getting mold experts in Indianapolis to look at the walls was the only thing that stopped the problem, and the logic holds anywhere: fix the room, then restock.
Keep offcuts honest
Offcuts are where good habits slip. Sort them by length into an open rack rather than a bin, burn or bin anything split or stained, and label the species on the end grain while you still remember it. A bin of jumbled offcuts in a corner traps moisture at the bottom and becomes a problem of its own.
A note on sheet goods
Plywood and MDF want to be stored on edge, slightly leaning, on a raised batten. Laid flat on a floor they bow, and the bottom sheet takes up moisture from the slab. Edge-sealing the most-used sheets with a coat of finish keeps them stable for longer.