All Things Wood

Warping

If it’s really bad:

• The bow / warp / crook / cup means the board is drier in some places than others. Milling will expose wet fibers that dry at a different rate than a non-milled side. You could wipe a damp cloth or rag on the inside of the bow and let it sit for a few hours. If it’s really bad you could wait overnight.
• When storing it, avoid leaving it flat on a table. Put some stickers (sticks of wood) underneath, evenly spaced so air can circulate all around.

During the Glue-Up

• Use Caulk. A long stiff straight piece of wood that you can clamp down over the seams, that will help keep the glue joint straight.
• Another option is to consider using the biscuit joiner to make space for biscuits. For this I might recommend clamping your board to a workbench so it is flat, then using the biscuit jointer to make your biscuit mortises. This should help with alignment during glue-up.

Preventative

Rough milling, closer to final milling, glue-ups, more material removal (sanding or planing)

• Rough milling. Rough mill, let the wood acclimate then mill again. Depending on how much material you’re removing, cutting away, planing, or jointing you may want to do multiple mill steps.
• Plan on removing material again after glue-ups as well. If you want your final dimension to be 3/4", give yourself some wiggle room of an extra 1/16" or more if you plan on a wild glue-up.

Time

The more time it has to acclimate in the space you’re working in the better your working experience will be. Keep projects in mind for where they’re going too. If you make something in the winter, expect that there will be some expansion by the time summer comes around.

Pulled from a Discourse post with additional information