This one is almost stupid, but it happens to still be helpful. On a through mortise you can center your work on a dog hole and some of the random chips will fall through it rather than get jammed into the bottom, where you will have to extricate them later.
And Now…a bonus tip!!!
When test fitting a mortise and tenon joint take care not to snag anything important…
You have been warned and so have I.
-- Make furniture that lasts as long as the tree - Ryan